Bio-feedback Apparatus

Abstract

An improved bio-feedback apparatus for sensing the brain-wave potentials produced by a subject wherein the sensed brain-wave potentials are processed through separate parallel processing channels of a controlling channel, each processing channel processing a preselected frequency range of the sensed brain-wave potential to provide subject-preceivable feedback signals indicative of signal presence within the preselected frequency of each processing channel. Each processing channel is constructed to provide predetermined signal amplitude and duration criteria for determining signal presence prior to initiating and terminating the feedback signals and, in one form, each processing channel is constructed to provide feedback signals indicative of the percentage of time during a subsequent predetermined epoch of time wherein a signal presence existed in the sensed brain-wave potential. In one form, the bio-feedback apparatus simultaneously produces audible feedback signals, each audible feedback signal having a separately identifiable tone indicative of signal presence within the preselected frequency range of the processing channels.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to improvements in bio-feedback apparatus and, more particularly, but not by way of limitation, to a bio-feedback apparatus for providing subject-perceivable feedback signals indicative of a controlled signal presence within preselected frequency ranges of a sensed brain-wave potential via separate parallel processing channels.

2. Description of the Prior Art

In the past there have been various devices constructed to sense brain-wave potentials, such devices being commonly referred to as electroencephalographic equipment, and the sensed brain-wave potentials being commonly referred to simply as "EEG" signals. In the simplest form, the brain-wave potentials are detected and the sensed potentials are plotted on a graph-type, read-out. Other devices have been constructed to sense the brain-wave potentials, and to utilize the sensed potentials or portions thereof for providing certain feedback indications.

VOLUNTARY DEVICE DISCLOSED IN THE PAST WAS DESCRIBED IN THE U.S. Pat. No. 3,548,812, issued to Paine. This patent disclosed an electroencephalographic apparatus for quantitatively measuring brain activity and utilizing the measured brain-wave activity for indicating a level of consciousness. The sensed brain-wave activity was amplified and passed through a bandpass filter having a passband generally between 0.7 Hz and 13.0 Hz, the filtered signal being subsequently fed through the three adjustable amplitude comparators having adjustable gain controls. Each of the amplitude comparators produced an output signal when the input signal was within the threshold setting of the amplitude comparator, the three output signals being utilized to generate signals indicative of various stages of sleep or consciousness and subsequently being fed through an analog adder.

The U.S. Pat. No. 3,032,029, issued to Cunningham, disclosed an apparatus for indicating the alertness of an individual and providing a means for stimulating the individual in response to a preset alertness level. The Cunningham apparatus utilized the alpha and the theta EEG signals which were passed through separate bandpass filters, threshold amplifiers, and diode rectifiers to the input of a coincidence circuit constructed to produce an output signal when the alpha and the theta signals were simultaneously applied thereto. The output of the coincidence circuit activated a remote warning and a random sequencer for enabling and disenabling a plurality of gates for activating various other warning devices such as a light stimulator, a sound stimulator and an electrical stimulator.

The U.S. Pat. No. 3,195,533, issued to Fischer, disclosed an apparatus for detecting physiological conditions wherein sensed electrical signals from spaced locations on an individual's body were fed through a filter for passing only certain frequency components and subsequently passed through a control circuit for providing an output signal having an average voltage responsive to the frequency of the sensed electrical signals. The control circuit of the Fischer apparatus generally included: a limiter means for controlling peak amplitude; a discriminator for providing a pulse for each reversal in polarity of the limiter output signal; and an integrator providing an output signal having an amplitude proportional to the average DC component of the pulses from the discriminator, the integrator output signal being utilized to control the output signal from the Fischer apparatus.

Various other devices for recording and analyzing EEG responses or the like are typlified in the U.S. Pat.: No. 2,860,627, issued to Harden; No. 2,848,992, issued to Pigeon; and No. 3,513,834, issued to Suzuki, for example.

SUMMARY OF THE INVENTION

An object of the invention is to provide a bio-feedback apparatus having an improved, more efficient and more accurate apparatus for developing feedback signals indicative of signal presence within preselected frequency ranges of a sensed brain-wave potential.

Another object of the invention is to provide an improved bio-feedback apparatus for simultaneously providing subject-perceivable and distinguishable audible feedback signals indicative of signal presence within preselected frequency ranges.

One other object of the invention is to provide a bio-feedback apparatus for simultaneously processing brain-wave potentials of a controlling channel through parallel processing channels for developing feedback signals indicative of signal presence in the processing channels.

Yet another object of the invention is to provide an improved bio-feedback apparatus for providing feedback signals indicative of the percentage of time during a predetermined epoch period of time wherein signal presence existed in the sensed brain-wave potential.

An additional object of the invention is to provide a bio-feedback apparatus having an improved apparatus for assuring signal presence within predetermined criteria prior to initiating feedback signals.

Another object of the invention is to provide a bio-feedback apparatus having an improved apparatus for assuring an absence of signal presence for a predetermined period of time prior to terminating feedback signals.

One additional object of the invention is to provide an improved bio-feedback apparatus for selectively providing feedback signals indicative of signal presence within controlled combinations of frequency ranges.

Another object of the invention is to provide an improved apparatus for selectively passing a signal component of a predetermined frequency range through separate processing channels.

A further object of the invention is to provide an improved bio-feedback apparatus which is more efficient and more economical in the construction and operation thereof.

Other objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawings which illustrate various embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatical view of a bio-feedback apparatus for producing feedback signals constructed in accordance with the present invention.

FIG. 2 is a diagrammatical view of another bio-feedback apparatus constructed to produce feedback signals, similar to the bio-feedback apparatus of FIG. 1.

FIG. 3 is a schematic, diagrammatical drawing showing the amplifier assembly and the sensitivity adjustment assembly of the bio-feedback apparatus of FIG. 2.

FIG. 4 is a schematic view showing a typical oscillator, one such oscillator being utilized in each of the processing channels of the bio-feedback apparatus of FIG. 2.

FIG. 5 is a schematic view of a typical control voltage generator, one such voltage control generator being utilized in each of the processing channels of the bio-feedback apparatus of FIG. 2.

FIG. 6 is a schematic view of the summing amplifier and the output indicator of the bio-feedback apparatus of FIG. 2.

FIG. 7 is a typical filter construction, one such filter being utilized in each of the processing channels of the bio-feedback apparatus of FIG. 2.

FIG. 8 is a diagrammatical view showing a filter response curve for a filter utilized in one of the processing channels constructed in accordance with the filter construction of FIG. 7.

FIG. 9 is a diagrammatical view showing a filter response curve for another filter utilized in one of the processing channels constructed in accordance with the filter construction of FIG. 7.

FIG. 10 is a diagrammatical view, similar to FIGS. 1 and 2, but showing yet another bio-feedback apparatus constructed to produce feedback signals.

FIG. 11 is a diagrammatical view of a portion of the feedback signal controller of the bio-feedback apparatus of FIG. 10.

FIG. 12 is a diagrammatical view of a portion of the data reduction controller of the bio-feedback apparatus of FIGS. 10 and 11.

FIG. 13 is a schematic, diagrammatical view of one signal input controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 14 is a schematic view of a portion of the feedback signal controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 15 is a schematic view of one zero crossing detector of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 16 is a schematic view of one amplitude discriminator, one comparator controller, and one automatic gain control of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 17 is a schematic view of one tachometer network of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 18 is a schematic view of one function generator constructed for a predetermined frequency range for utilization with one tachometer network, constructed as typically shown in FIG. 17, in the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 19 is a schematic view, similar to FIG. 18, but showing one other function generator constructed for a predetermined frequency range for utilization with one tachometer network, constructed as typically shown in FIG. 17, in the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 20 is a schematic view of one voltage controlled oscillator, one signal converter, and a position of one interconnecting network between a signal converter and an automatic gain control of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 21 is a schematic view of one bandpass controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 22 is a schematic view of a portion of one audio output controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 23 is a schematic view of a portion of one audio output controller and a portion of one audio output indicator of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 24 is a schematic view of one analog switch of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 25 is a diagrammatical, schematic view of one overvoltage controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 26 is a diagrammatical, schematic view of one portion of a counter controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 27 is a schematic view of one digital/analog converter of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 28 is a diagrammatical, schematic view of one portion of a counter controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 29 is a diagrammatical, schematic view of one portion of one visual output controller and one associated visual output indicator of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 29, is a diagrammatical, schematic view, similar to FIG. 29, but showing one other portion of one visual output controller and one associated visual output indicator of the bio-feedback apparatus of FIGS. 19, 11 and 12.

FIG. 31 is a schematic view of a portion of one visual output controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in general, and to FIG. 1 in particular, shown therein and designated by the general reference numeral 10, is a bio-feedback apparatus for sensing and detecting physiological and psychophysiological states and changes of a particular subject and providing subject-perceivable feedback indications of the sensed physiological and psychophysiological variables which is particularly useful in phychophysiological research and training. More particularly, the bio-feedback apparatus 10 is useful in inducing, promoting, sensing and detecting certain physiological and psychophysiological variables related to and indicative of various internal states and conditions such as, for example, "attention," "consciousness," "thought," "creativity" and levels of various emotions, and for teaching and enhancing voluntrary control of these various internal states and conditions in a manner which will be made more apparent below.

In general, the bio-feedback apparatus 10 includes: a sensing assembly 12 detecting and sensing various physiological and psychophysiological states and conditions of a subject and providing an output electrical signal 14 responsive thereto; a frequency discriminator 16 receiving the output signal 14 and providing a plurality of output signals 18, each frequency discriminator output signal 18 being indicative of the presence of a signal within a preselected, discrete frequency band in the sensing assembly output signal 14; a feedback signal controller 20 for receiving and processing the received frequency discriminator output signals 18, each output signal 18 being processed in parallel through separate, distinct processing channels of the frequency discriminator 16 and the feedback signal controller 20 for selectively providing predetermined, selected output signals 22 and 24 from the feedback signal controller 20; a subject feedback controller 26 receiving the feedback signal controller output signal 22 and providing a subject-perceivable output indication indicative of signal presence of the predetermined, preselected, sensed physiological and psychophysiological states and conditions; and a permanent feedback indicator 28 receiving the feedback signal controller output signal 24 and providing a permanent-type of output indication indicative of signal presence of the predetermined, preselected, sensed physiological and psychophysiological states and conditions. The bio-feedback apparatus 10 is constructed to provide a fast, convenient, efficient, positive, and selectively controlled apparatus providing various predetermined, controlled, immediate, subject-perceivable and permanent feedback indications of sensed physiological and psychophysiological states and conditions for subject training and conditioning in the general area of volitional control of various internal states and conditions and for evaluation and analysis to define more finite correlations between the various sensed physiological and psychophysiological states and conditions of one particular subject or particular groups of subjects.

The activity of various areas of an individual's brain has been associated with identifiable and definable conscious and unconscious states and conditions, and it has been determined that subjects can be trained to varying degrees to control both active and passive volitional aspects of the subject's nervous system, for example. It should also be noted that various physiological and psychophysiological internal states and conditions have been correlated and identified with particular frequency components of the sensed potentials produced by as individual's brain. For example, the four major frequency bands are generally referred to as: the "Delta" band having an approximate frequency band generally from 0.5 Hz. to 4.0 Hz.; the "Theta" band having an approximate frequency band generally from 4.0 Hz. to 8.0 Hz.; the "Alpha" band having an approximate frequency band generally from 8.0 Hz. to 13.0 Hz.; and the "Beta" band having an approximate frequency band generally from 13.0 Hz. to 26.0 Hz. Each of these frequency bands has been identified and associated with a particular physiological or psychophysiological state or condition and, in some instances, it has been determined that the presence of two or more of the frequency bands is also indicative of a predetermined or identifiable physiological or psychophysiological state or condition.

In the past, devices have been developed for measuring and recording the rhythmetically varying potential produced by an individual's brain, the potential being sensed or detected by electrodes applied to preselected portions of the individual's scalp and the devices were generally constructed to receive the sensed potential and provide a chart-type of output indicative thereof. Apparatus of the type referred to above is generally known as an electroencephalograph, and the brain-wave signals which were sensed and recorded by the electroencephalograph are commonly referred to by the letter designations "EEG."

In a preferred form, the bio-feedback apparatus 10, shown in FIG. 1, is constructed to sense the varying potential produced by the activity of an individual's brain, and to provide the various feedback indications indicative of or in response to the presence of predetermined portions of the sensed varying potential. The sensing apparatus 12, more particularly, includes a brain-wave indicator 30 having a portion connected to sense and detect the varying potentials produced by the individual's brain and provide an output signal 32 responsive thereto and indicative thereof; and a brain-wave signal generator 34 receiving the brain-wave indicator output signal 32 and providing the amplified output signal 14 responsive thereto indicative of the sensed brain-wave potential, as mentioned before. In one form, the brain-wave indicator 30 includes a number of electrodes which are attached to the individual's scalp, the electrodes being constructed, attached and positioned to sense the brain-wave potential produced by the subject and provide the output signal 32. Since the sensed potentials produced by an individual's brain are of a small amplitude, the brain-wave signal generator, more particularly, receives the electrodes' output signal 32 and provides an amplified output signal 14.

In one form, the brain-wave indicator 30 is attached to the subject to sense brain-wave potentials from two or more preselected portions of the individual's scalp, thereby providing two or more distinct brain-wave potentials to the input of the brain-wave signal generator 34. In this form, the brain-wave signal generator 34 is constructed such that one of the sensed brain-wave potentials is selectively provided at the brain-wave signal generator output signal 14; the distinct, sensed brain-wave potentials each being referred to below as "channels" and the brain-wave potential selected via the brain-wave signal generator 34 for controlling the feedback indications being referred to below as the "controlling channel."

The controlling channel signal 14 is connected to the frequency discriminator 16, the frequency discriminator 16 selectively detecting predetermined frequency components of the controlling channel signal 14 for processing through separate, parallel "processing channels" of the bio-feedback apparatus 10. Thus, each processing channel of the bio-feedback apparatus 10 processes one frequency component, defined by the predetermined passbands of the frequency discriminator 16, and each processing channel is processed via the feedback signal controller 20 to develop and generate the feedback signals 22 and 24. The processing of the preselected frequency components of the detected, received brain-wave potential via parallel processing channels of the feedback signal controller 20 allows the various components and assemblies of the bio-feedback apparatus 10 to be sized and constructed for processing a single preselected signal having a predetermined frequency band, thereby facilitating the construction and design of a more efficient, more accurate signal processing assembly for indicating signal presence of a particular frequency component in the detected brain-wave potential. The utilization of separate signal processing channels for the various predetermined, preselected frequency components also provides a bio-feedback apparatus 10 which has a substantially higher stability and, in general, a more selective type circuitry for providing preselected, controlled feedback signals, yet eliminating undesirable artifacts such as those commonly referred to in the art as "EEG spike discharges," eye blinks, muscle artifacts, twitches, and the like, for example.

In one preferred embodiment, brain-wave potentials are detected and sensed at two, preselected scalp sites, and the two sensed, brain-wave potentials are processed in parallel through the bio-feedback apparatus via separate channels, each channel including a plurality of parallel processing channels. In this embodiment, the two channels are each utilized to provide subject-perceivable audio feedback in a monaural or stereo form, and one channel is utilized for control of the artifacts generated in the sensed brain-wave potentials and for control of subject-perceivable feedback presented in a visual and permanent form, as will be made more apparent below.

Electrodes are attached to the subject for detecting and sensing the brain-wave potentials and, initially, two scalp sites on the individual's head are selected (preferably on opposite sides of the subject's head and generally in the occipital areas) and the electrodes are attached at these preselected scalp sites. In general, the preselected scalp sites are cleaned with an alcohol, electrode paste which is rubbed into the skin to remove the horny layer and permeate the dermal surface with a conductive medium, the electrode paste being utilized to generally assure a low electrode resistance for facilitating the production of a low-noise signal for subsequent processing by the bio-feedback apparatus 10. The electrodes can be applied to the preselected scalp sites by using a Bentonite clay mixture or the like covered by a plastic film, the plastic film being utilized to prevent or substantially reduce the drying tendency of the clay mixture. In one form, the subject's left ear lobe and right ear lobe are then tied together for use as a reference for monopolar recording of the brain-wave potential. Finally, the electrode attachment is made by rubbing in a salt paste or the like and attaching an ear clip electrode (generally filled with salt paste) to the ear. The ground or neutral is attained via a plate electrode attached to a portion of the subject's wrist, for example. The use of electrodes and the attachment of the electrodes to various portions of the subject to detect brain-wave potentials, as generally described before, is well known in the art. It should be noted, however, that the electrodes may be attached to particular portions of the individual's scalp to obtain a particular brain-wave potential for processing by the bio-feedback apparatus 10.

Description of FIGS. 2 Through 9

Shown in FIGS. 2 through 9 is a bio-feedback apparatus 10a having: a brain-wave indicator 30a producing an output signal 32a indicative of the individual's brain-wave potential; a brain-wave signal generator 34a; a frequency discriminator 16a; and a feedback signal controller 20a. As diagrammatically shown in FIG. 2, the brain-wave indicator 30a generally includes: a reference electrode 38 providing an output signal 40; a neutral electrode 42 providing an output signal 44; and an active electrode 46 providing an output signal 48. The reference electrode 38, the neutral electrode 42, and the active electrode 46 are, in a preferred form, each attached to preselected scalp sites of the subject for detecting and sensing brain-wave potentials, in a manner as generally described before. More particularly and for example, the reference electrode 38 can be attached to the subject's left ear lobe, the neutral electrode 42 can be attached to the subject's right ear lobe, and the active electrode 46 can be attached to a predetermined scalp site on the individual's head such as the left occipital area or the right occipital area of the individual's head, it being understood that the particular electrodes utilized and the particular attachment sites of the electrodes on the subject are determined in each application such that the electrodes 38, 42 and 46 detect and sense particular, preselected brain-wave potentials.

The output signals 40, 44 and 48 of the electrodes 38, 42 and 46 are each connected to and received by a portion of the brain-wave signal generator 34a. As shown in FIG. 2, the brain-wave signal generator 34a, more particularly, includes: a receiver control 50 connected to the electrodes 38, 42 and 46 to receive the output signals 40, 44 and 48, respectively, therefrom and to provide an output signal 52 in response to the received signals 40, 44 and 48; a preamplifier 54 which is connected to the receiver control 50 receiving the receiver control output signal 52 and providing an amplified output signal 56 in response thereto; an amplifier assembly 58, having a plurality of amplifiers, each amplifier receiving the amplified output signal 56 and providing an amplified output signal in response to the received preamplifier output signal 56; and a sensitivity adjustment assembly 60 having a portion connected to each amplifier of the amplifier assembly 58 for adjusting the threshold level of each amplifier. The frequency discriminator 16a includes a filter assembly 62 having a filter receiving the amplified output signal from the amplifier assembly 58, each filter selecting and passing signals within a predetermined frequency range. The feedback signal controller 20a includes: a control voltage generator assembly 64 having one portion connected to one of the filters of the filter assembly 62, each portion receiving the filter output signal from one of the filters of the filter assembly 62 and developing a feedback control voltage indicating predetermined signal presence within the frequency band of the filter connected thereto; an oscillator assembly 66 having one portion connected to a portion of the control voltage generator assembly 64 for receiving the feedback control voltages developed via the control voltage generator assembly 64, the oscillator assembly 66 providing a plurality of oscillator output signals in response to a predetermined, received feedback control voltage from the control voltage generator assembly 64, each oscillating output signal having an identifiable frequency indicative of a signal presence within a preselected frequency range; a volume control assembly 68 receiving the output signals from the oscillator assembly 66, and selectively and adjustingly controlling the volume of each signal; an on-off control assembly 70 interposed between the oscillator assembly 66 and the volume control assembly 68 for selectively passing predetermined oscillating output signals from the oscillator assembly 66; a summing amplifier 72 receiving the oscillating output signals connected thereto via the on-off control assembly 70 and providing an output signal 74 in response to the received input signals; and an output indicator 76 receiving the summing amplifier output signal 74 and providing a subject-perceivable feedback indication responsive to the received signal from the summing amplifier 72.

As shown in FIG. 2, the electrodes 38, 42 and 46 are connected to the subject such that a single brain-wave potential is sensed and detected; the single, sensed brain-wave potential constituting the controlling channel of the bio-feedback apparatus 10a. The bio-feedback apparatus 10a includes three processing channels 78, 80 and 82, each processing channel 78, 80 and 82 receiving the preamplifier output signal 56 and developing a feedback signal indicative of a controlled, predetermined signal presence.

The amplifier assembly 58, more particularly, includes an Alpha amplifier 84, a Beta amplifier 86, and a Theta amplifier 88; the Alpha amplifier 84 receiving the preamplifier output signal 56 and providing an amplified output signal 90 in response thereto; the Beta amplifier 86 receiving the preamplifier output signal 56 and providing an amplifier output signal 92 in response thereto; and the Theta amplifier 88 receiving the preamplifier output signal 56 and providing an amplifier output signal 94 in response thereto.

An Alpha sensitivity adjustment 96 is connected to the Alpha amplifier 84 to receive the amplified output signal 90 therefrom and to provide an output signal controlling the threshold level of the Alpha amplifier 84; a Beta sensitivity adjustment 98 is connected to the Beta amplifier 86 to receive the amplified output signal 92 therefrom and provide an output signal for controlling the threshold level of the Beta amplifier 86; and a Theta sensitivity adjustment 100 is connected to the Theta amplifier 88 to receive the amplified output signal 94 therefrom and provide an output signal for controlling the threshold level of the Theta amplifier 88. The Alpha sensitivity adjustment 96, the Beta sensitivity adjustment 98 and the Theta sensitivity adjustment 100 are each part of the sensitivity adjustment assembly 60, each of the sensitivity adjustments 96, 98 and 100 controlling the threshold level of the amplifier 84, 86 and 88 connected thereto, during the operation of the bio-feedback apparatus 10a.

The filter assembly 62 includes an Alpha filter 102, a Beta filter 104 and a Theta filter 106. The Alpha filter 102 is connected to the Alpha amplifier 84 to receive the amplified output signal 90, the Alpha filter 102 being constructed, in one form, to have a pass band in the range of approximately 8.3 Hz. to 13.0 Hz. The Beta filter 104 is connected to the Beta amplifier 86 for receiving the amplified output signal 92, and is constructed, in one form, to have a pass band in the range of approximately 14.0 Hz. to 26.0 Hz. The Theta filter 106 is connected to the Theta amplifier 88 to receive the amplified output signal 94, and is constructed to have a pass band in the range of approximately 4.0 Hz. to 7.7 Hz. The Alpha filter 102, the Beta filter 104 and the Theta filter 106 each have an output signal 108, 110 and 112, respectively, and each output signal 108, 110 and 112 is a signal having a frequency within the pass band of the filter connected thereto, the filter output signals 108, 110 and 112 thereby indicating the signal presence in the sensed, detected brain-wave potential of a discrete, predetermined frequency band (corresponding to the pass band of the particular filter).

The control voltage generator assembly 64, more particularly, includes an Alpha control voltage generator 114, a Beta control voltage generator 116 and a Theta control voltage generator 118. The Alpha control voltage generator 114 receives the Alpha filter output signal 120 in response thereto indicating signal presence of a signal having a frequency generally between 8.3 Hz. and 13.0 Hz. (the pass band of the Alpha filter 102). The Beta control voltage generator 116 receives the Beta filter output signal 110 and produces a feedback control signal 122 in response thereto indicating signal presence of a signal having a frequency generally between 14.0 Hz. and 26.0 Hz. (the pass band of the Beta filter 104). The Theta control voltage generator 118 receives the Theta filter output signal 112 and provides a feedback control signal 124 in response thereto indicating signal presence of a signal having a frequency generally between 4.0 Hz. and 7.7 Hz. (the pass band of the Theta filter 106).

The oscillator assembly 66 includes an Alpha oscillator 126, a Beta oscillator 128 and a Theta oscillator 130. The Alpha oscillator 126 receives the feedback signal 120 from the Alpha control voltage generator 114 and provides an oscillating output signal 132 in response thereto; the Beta oscillator 128 receives the feedback control signal 122 of the Beta control voltage generator 116 and provides an oscillating output signal 134 in response thereto; and the Theta oscillator 130 receives the feedback control signal 124 from the Theta control voltage generator 118 and provides an oscillating output signal 136 in response thereto.

In a preferred form, the Alpha oscillator 126 is constructed to provide an output signal 132 having a frequency of approximately 800 Hz.; the Beta oscillator 128 is constructed to provide an output signal having a frequency of approximately 1100 Hz.; and the Theta oscillator 130 is constructed to provide an output signal having a frequency of approximately 600 Hz. The last-mentioned frequencies of the output signals 132, 134 and 136 of the oscillators 126, 128 and 130, respectively, were selected, in one operational embodiment, to provide audible, subject-perceivable feedback signals which can be identified when simultaneously presented via the output indicator 76.

The volume control assembly 68 includes volume controls 138, 140 and 142 receiving the oscillating output signals 132, 134 and 136, respectively, each of the volume controls 138, 140 and 142 being constructed to adjust the "loudness" of the output signals 132, 134 and 136 connected thereto. The on-off control assembly 70 includes on-off controls 144, 146 and 148, each being interposed generally between one of the oscillators 126, 128 and 130 and one of the volume controls 138, 140 and 142, connected thereto, as shown in FIG. 2. Each of the on-off controls 144, 146 and 148 is constructed to connect and disconnect the output signal of the oscillator connected thereto in the "on" and the "off" positions, respectively, of the on-off controls 144, 146 and 148. In this manner, the feedback indications provided by the bio-feedback apparatus 10a can be selectively controlled such that any one of the oscillators 126, 128 and 130 or any combination of the oscillators 126, 128 and 130 can be connected to the summing amplifier 72 and utilized to provide feedback indications for training a subject or for indicating particular physiological and psychophysiological states of the subject.

In summary, the processing channel 78 includes the Alpha amplifier 84, the Alpha sensitivity adjustment 96, the Alpha filter 102, the Alpha control generator 114, the Alpha oscillator 126, the volume control 138 and the on-off control 144. In a similar manner, the processing channel 80 includes the Beta amplifier 86, the Beta sensitivity adjustment 98, the Beta filter 104, the Beta control voltage generator 116, the Beta oscillator 128, the on-off control 146 and the volume control 140; and the processing channel 82 includes the Theta amplifier 88, the Theta sensitivity adjustment 100, the Theta filter 106, the Theta control voltage generator 118, the Theta oscillator 130, the on-off control 148 and the volume control 142. The various components and assemblies of the processing channels 78, 80 and 82 cooperate to develop and provide the feedback signals 132, 134 and 136, respectively, to the summing amplifier 72 indicating the presence of a signal having a frequency within the pass band of the Alpha filter 102, the Beta filter 104, and the Theta filter 106, respectively.

The output signal 72 of the mixer or the summing amplifier 72 is indicative of and contains the oscillating output signals 132, 134 and 136, in an "on" position of the respective on-off controls 144, 146 and 148, the summing amplifier output signal 74 being a mix of the oscillator output signals 132, 134 and 136. The output indicator 76 is constructed to provide subject-perceivabile audible and visual output indications indicative of signal presence at predetermined criteria and having a frequency within the pass band of the processing channels 78, 80 and 82.

It should be particularly noted that other processing channels, similar to the processing channels 78, 80 and 82 can be incorporated in the bio-feedback apparatus 10a to provide a feedback indicative of signal presence of signals having frequencies within frequency band ranges other than the Alpha band, the Beta band, and the Theta band, described before. The additional processing channels can be connected in parallel with the processing channels 78, 80 and 82, described before, each additional channel generally including the various components and assemblies identified with and connected in the processing channels 78, 80 and 82, described above.

Referring more particularly to the receiver control 50, as shown in FIG. 2, the receiver control 50, in a preferred form, can include a switching network interposed between the electrode output signals 40, 44 and 48 and the preamplifier 52 for selectively connecting the reference electrode 38, the neutral electrode 42 and the active electrode 46 into various portions of an electrode resistance check network wherein the resistance between the reference electrode 38 and the neutral electrode 42 can be measured, in one switch position, and the electrode resistance generally between the reference electrode 38 and the active electrode 46 can be measured, in one other switch position, for example. In this form, a battery type supply voltage, for example, can be connected across the electrodes and a resistance type network can be interposed between the electrodes being tested and a meter such that the meter provides an output indication of the electrode resistance, thereby assuring that the electrical resistances of the electrodes 38, 42 and 46 are within operable tolerance limits before switching the receiver control 50 to an operate position wherein the output signals 40, 44 and 46 of the electrodes are connected to the preamplifier 54.

The bio-feedback apparatus 10a, as shown in FIG. 2, is particularly constructed to provide a compact, portable feedback type of apparatus and, in this form, the operating supply voltages for the various components and assemblies of the bio-feedback apparatus 10a would be supplied via a battery type of power supply. In this form, the receiver control 50 can also be constructed to include a switch position for connecting the batteries to a meter type indicator for checking the operating condition of the batteries, and a built-in battery recharger unit can also be incorporated with the bio-feedback apparatus 10a.

The preamplifier 54 is, in a preferred form, a differential, fixed gain type of preamplifier having a low noise level and constructed to receive low amplitude signals from the electrodes 38, 42 and 46. Preamplifiers of this type are commercially available, and the construction and operation of such preamplifiers is well known in the art.

As shown in FIG. 3, and, as generally described before, the preamplifier output signal 56 is applied to the input of three amplifiers or, more particularly, to the input of the Alpha amplifier 84, the input of the Beta amplifier 86, and the input of the Theta amplifier 88, the amplifiers 84, 86 and 88 each being connected in parallel for receiving the preamplifier output signal 56. The ground connection is provided via a resistor 150, as shown in FIG. 3.

In one form, the Alpha amplifier 84, the Beta amplifier 86 and the Theta amplifier 88 are each of the integrated circuit type of construction and a positive power supply (not shown) is connected to each amplifier 84, 86 and 88 via the pin connections 152 and a negative power supply (not shown) is connected to each amplifier 84, 86 and 88 via the pin connections 154. In this form, a resistor 156 connected in series with a capacitor 158, the resistor 156 and the capacitor 158 being connected to the internal components of each amplifier 84, 86 and 88, and a resistor 160 connected in series with a capacitor 162 and in parallel with a capacitor 164 is also connected to the internal components of each ampoifier 84, 86 and 88 for frequency compensation of the amplifiers 84, 86 and 88, the capacitor 164 being also conected to the respective amplifier output signal, as shown in FIG. 3. Each amplifier 84, 86 and 88 also includes a feedback loop 165 between the amplifier output signal and the negative input differential signal to each of the amplifiers 84, 86 and 88, and a pair of diodes 166 and 168 are interposed in each feedback loop. The negative differential input to the amplifiers 84, 86 and 88 is connected to ground via a resistor 170 interposed in each ground connection.

An additional feedback loop 172 is connected between the input signal 56 and the output signal of each amplifier 84, 86 and 88, and a resistor 174 and a variable resistor 176 are interposed in each feedback loop 172. As shown in FIG. 3, the feedback loop 174 is parallel to and generally included within the feedback loop 165. Each of the amplifiers 84, 86 and 88 is generally a differential type of amplifier having two input circuits, one input circuit being the preamplifier output signal 56 and the other input circuit being controlled via the feedback loops 156 and 172 and, more particularly, being controlled via the variable resistor 176 interposed in the feedback loop 172 therein. The feedback loops 172 and the variable resistor 176 interposed therein constitute the sensitivity adjustments 96, 98 and 100 connected to the amplifiers 84, 86 and 88. Each amplifier 84, 86 and 88 thus responds to the difference between the two input circuits connected thereto, and the sensitivity adjustments 96, 98 and 100 essentially constitute the gain control for amplifiers 84, 86 and 88, the gain controls or sensitivity adjustments 96, 98 and 100 being, in a preferred form, calibrated in peak-to-peak microvolts and used as threshold sensitivity adjustments for the frequency bands processed through the various processing channels 78, 80 and 82.

Thus, by selectively adjusting the variable resistors 176 of the sensitivity adjustment assembly 60, the differential amplifiers 84, 86 and 88 are each adjusted to receive and amplify an input signal controlled by the threshold level setting of the sensitivity adjustment assembly 60 and to reject the preamplifier output signals 56 which do not exceed the minimum threshold level setting of the sensitivity adjustment assembly 60, thereby assuring amplified output signals 90, 92 and 94 from the amplifiers 84, 86 and 88 of a minimum amplitude and assuring that the bio-beedback apparatus 10 will provide feedback signals only when receiving input signals thereto of a minimum amplitude.

The amplifier output signals 90, 92 and 94 are fed through the Alpha filter 102, the Beta filter 104 and the Theta filter 106, respectively, each filter 102, 104 and 106 selecting and passing only those portions of the input signal having a frequency within the pass band of the particular filter, as described before. Each filter 102, 104 and 106 is, more particularly, an active, bandpass type of filter having an elliptical response. A filter construction, typical of the construction of the Alpha filter 102, the Beta filter 104 and the Theta filter 106, is shown in FIG. 7, and the filter basically comprises three cascaded, infinite-gain universal type active filter sections (referred to in FIG. 7 as a first active filter stage 180, a second active filter stage 182, and a third active filter stage 184). The input signal 90 or 92 or 94 to the filters 102, 104 and 106, respectively, is connected to the first filter stage 180 via a first feedback network comprising the resistors 186, 188 and 190 and a capacitor 192. The feedback network connected to the first filter stage 180 is constructed to produce a frequency function (jw) axis of zero, forming an elliptic function characteristic outside the pass band at the lower frequency (f.sub.L) of the filter pass band. The first filter stage 180, in a preferred form, has a relatively low "Q" bandpass function with its resonant frequency (f.sub.o) at the resonant frequency of the filter 102, 104 or 106 ("Q" being a quality factor which generally indicates the sharpness of frequency sensitivity of the filter).

The output of the first filter stage 180 is connected to the second filter stage 182 via a conductor 194 through a second feedback network comprising the resistors 196, 198 and 200 and the capacitor 202, the second feedback network producing a frequency function (jw) axis for the elliptic function characterisitc outside the filter pass band on the upper frequency (f.sub.u) side of the filter pass band. The second filter stage 182 is, in a preferred form, constructed to have a relatively medium Q bandpass function having its (the second filter stage 182) resonant frequency (f.sub.o) just below the upper frequency (f.sub.u) response of the filters 102, 104 and 106.

The output of the second filter stage 182 is coupled to the third filter stage 184 via conductor 204, the output of the third filter stage 184 being the filter output signals 108 or 110 or 112 of the filters 102, 104 or 106, respectively. The third filter stage 184 is, in a preferred form, an adjustable gain, relatively medium Q bandpass function, with its (the third filter stage 184) resonant frequency located jsut above the lower frequency (f.sub.L) response of the filters 102, 104, 106. It should also be noted that, in one other form, the positioning of the second filter stage 182 and the third filter stage 184 can be reversed with respect to the diagrammatical, schematic showing of the typical filter construction in FIG. 7, without substantially effecting the total filter response.

The filter construction, as shown in FIG. 7 and described above, is constructed to provide a filter having a relatively low pass band ripple and a substantially high or sharp rolloff rate outside the pass band, thereby providing a selective filter response to obtain a sharp channel separation between the frequency bands selected and passed by the Alpha filter 102, the Beta filter 104 and the Theta filter 106 for processing through the parallel processing channels 78, 80 and 82, respectively, of the bio-feedback apparatus 10b.

In one operational application, for example, an Alpha filter 102, constructed in a manner as described in connection with the typical filter construction shown in FIG. 7, and designed to pass signals having frequencies from approximately 8.0 Hz. to 13.0 Hz. has been tested to have a filter response curve substantially as shown in FIG. 8, and a Theta filter 106, constructed in accordance with the typical filter construction shown and described with respect to FIG. 7, has been tested to have a filter response curve substantially as shown in FIG. 9, wherein the Theta filter was designed to pass signals having a frequency from approximately 4.0 Hz. to 7.0 Hz. In this operational example, the voltage input to the Alpha filter and the Theta filter was approximately 0.5 volts (peak-to-peak) and the output voltage of the Theta filter and the Alpha filter was approximately 2.0 volts (peak-to-peak).

The Alpha filter 102 response curve, shown in FIG. 8, indicates a flat-band response from approximately 8.0 Hz. to approximately 12.8 Hz., and, from the minus 2.5 db points to the notches of the Alpha filter 102, the Alpha filter 102 had a rolloff rate of approximately 30.0 db per one-half cycle, the pass band having approximately a 0.8 db maximum ripple within the pass band.

The Theta filter 106 response curve, shown in FIG. 9, indicates a flat-band response from approximately 4.2 Hz. to 7.9 Hz., the Theta filter 106 having an equally sharp roll-off rate at the minus 2.5 db points and an equally minimum ripple within the pass band, as shown by the Theta filter response curve.

It should also be noted that the bio-feedback apparatus 10a is constructed such that, when signals are being processed within the Theta band (approximately 4.0 Hz. to 8.0 Hz.) have a frequency of approximately 8.0 Hz., the Theta filter response is down to approximately 2.5 db; but, at a frequency of 9.0 Hz., the Theta filter response is down to approximately 30 db, thereby providing a minimum overlap between the frequency bands being processed via the various processing channels of the bio-feedback apparatus 10a. When the db level is down to approximately 10.0 db, the feedback in that particular processing channel is substantially lost or, in other words, the signal is not of a sufficient strength to indicate a signal presence in that particular processing channel. It should be noted, however, that ther will be feedback in the other processing channels, assuming a signal presence within the frequency range or band width of the particular processing channel. Thus, the filters 102, 104 and 106 are each constructed and designed to select and finally separate the amplified incoming signals into distinct, separate processing channels with a minimum processing channel signal overlap, the signal overlap being approximately 1.0 cycle wide, in the operational example described above.

A typical control voltage generator which can be utilized as the Alpha, the Beta or the Theta control voltage generators 114, 116 or 118 (shown in FIG. 2) is shown in FIG. 5, and includes: a phase splitter network 208; a rectifier network 210; and a timing network 212, the operating power supply (not shown) being provided to the control voltage generators 114, 116 and 118 via a pin connection 214.

The phase splitter network 208 generally consists of a pair of resistors 216 and 218 connected to the junction 220 and a transistor amplifier 222, the base of the transistor amplifier 222 being connected to the junction 220. The phase splitter network 208 is generally constructed for receiving an input signal 108, 110 or 112, respectively, from the Alpha filter 102, the Beta filter 104 or the Theta filter 106, respectively, and providing two output signals or waves having different phases or differing in phase relationship. Each input signal 108, 110 or 112 is coupled in one phase splitter network 208 via a capacitor 224, and one of the phase splitter network output signals is coupled to the rectifier network 210 via a capacitor 226, the other phase splitter network output signal being coupled to the rectifier network 210 via a capacitor 228. The phase splitter network 208 also includes a resistor 230 connected generally between the collector of the transistor amplifier 222 and the operating power supply (not shown) connected to the pin connection 214 and a resistor 235 connected generally between the emitter of the transistor amplifier 222 and ground.

The rectifier network 210 consists of four diodes connected to form a full-wave diode bridge type of rectifier network, one junction of the diode bridge receiving one of the phase splitter network output signals via the capacitor 226 and one other junction of the diode bridge receiving the other phase splitter network output signal via the capacitor 228. The input signals to the diode bridge are connected to two of the diode bridge junctions, one of the diode bridge junctions, not connected to receive a phase splitter network output signal, is connected to ground, the other diode bridge junction, not connected to receive a phase splitter network output signal, is connected to an output pin connection providing the output signals 120, 122 or 124 of the control voltage generator assembly 64, as indicated in FIGS. 2 and 5.

The timing network 212 includes a cpacitor 236 connected in parallel with a resistor 238, the timing network 212 being interposed generally between the rectifier network 210 and the output signal pin connection of the control voltage generator. The feedback control signal 120 or 122 or 124 of the control voltage generators 114 or 116 or 118, respectively, are thus processed through the phase splitter network 208 and through the full-wave diode bridge rectifier network 210 and finally through the timing network 212, the feedback control 120, 122 and 124 being produced via the control voltage generators 114, 116 and 118, after a predetermined time delay controlled by the time constant determined by the values of the capacitor 236 and the resistor 238 of the timing network 212. The capacitor 236 and the resistor 238 of the timing network 212 are each sized to provide a charge and discharge time constant such that a predetermined number of cycles of the filter output signals 108, 110 and 112 are requried subsequent to the feedback control voltages 120, 122 and 124, respectively, being produced at the output of the respective control voltage generators 114, 116 and 118, thereby assuring a signal presence within one of the processing channels 78, 80 and 82 for a predetermined, minimum period of time subsequent to a feedback signal being produced by the bio-feedback apparatus 10a. In this manner the bio-feedback apparatus 10 substantially eliminates feedback signals being produced via a single, short duration, relatively high amplitide, sensed potential, such as signals which might be produced via muscle artifacts or the like, for example.

Thus, the sensitivity adjustment assembly 60 and the control voltage generator assembly 64 cooperate to determine and set signal criteria for each of the processing channels 78, 80 and 82 such that an input signal must have a minimum amplitude and exist for a predetermined, minimum period of time subsequent to the feedback control signals 120, 122 and 124 being initiated or generated within the particular processing channels 78, 80 and 82. The feedback control signals 120, 122 and 124 are, more particularly, d-c control votlages, and are utilized to activate the oscillator connected thereto.

A typical oscillator 126, 128 or 130 is shown in FIG. 4, and the feedback control signals 120 or 122 or 124 are, more particularly, connected to the base of a switching transistor 240 via a resistor 242. The emitter of the switching transistor 240 is connected to ground and the collector of the switching transistor is connected to an oscillator network 244 via a resistor 246. The switching transistor 240 is constructed to be normally biased in the "off" position, and to be biased in the "on" position when the feedback control signal 120 or 122 or 124 is applied thereto, thereby biasing or activating the oscillator network 244 in the "on" position, in a manner to be described in greater detail below.

The oscillator network 244 basically consists of a pair of transistor amplifiers 248 and 250, the collector of the transistor amplifier 248 being connected to an operating power supply (not shown) via a pin connection 252 and the emitter of the transistor amplifier 248 being connected to the collector of the switching transistor 240 via the resistor 246. The collector of the transistor amplifier 250 is connected to the operating power supply (not shown) via the pin connection 252 and the emitter of the transistor amplifier 250 is connected to ground via a resistor 254. A resistor 256 is interposed between the transistor amplifier 248 an the pin connection 252, and a resistor 258 is interposed between the collector of the transistor 250 and the pin connection 252, as shown in FIG. 4. A variable resistor 260 is interposed between the collector of the transistor amplifier 248, and, more particularly, between the resistor 256 and the pin connection 252, and the base of the transistor amplifier 248 is connected to the collector of the transistor amplifier 250 via a resistor 262, a capacitor 264 being connected between the base of the transistor amplifier 248 and the emitter of the transistor amplifier 250. The collector of the transistor amplifier 248 is also connected to the base of the transistor amplifier 250 via a capacitor 268, and the emitter of the transistor amplifier 248 is also connecced to the base of the transistor amplifier 250 via a variable resistor 270.

The transistor amplifiers 248 and 250, as shown in FIG. 4, and the interconnecting capacitive-resistive network therebetween form the oscillator network 244, the output signal of the oscillator network 244 having a frequency determined by the sizes of the various componets of the oscillator network 244, as well known in the art. The variable resistor 260 is connected in the oscillator network 244 to variably and selectively control the amplitude of the oscillator output signal, and the variable resistor 270 is connected in the oscillator 244 to variably and selectively control the frequency of the oscillator output signal in an operating mode or activated position of the oscillator network 244, during the operation of the bio-feedback apparatus 10a. In one preferred operational embodiment, the Alpha oscillator 126 is constructed to generate and provide an output signal having a frequency of 800 Hz.; the Beta oscillator 128 is constructed to generate and provide an output signal having a frequency of 1100 Hz.; and the Theta oscillator 130 is constructed to generate and provide an output signal frequency of 600 Hz., as mentioned before.

The oscillating output signals 132, 134 or 136 are connected to the on-off controls 144, 146 and 148, respectively, via a capacitor 276 connected on one end thereof to the emitter of the transistor amplifier 250, generally between the connection of the capacitor 264 to the emitter of the transistor amplifier 250 and the resistor 254, the on-off controls 144, 146 and 148 being schematically shown in FIG. 4 as an on-off type of switch. The on-off controls 144, 146 and 148 are each connected to one of the volume controls 138, 140 or 142 (the volume controls 138, 140 or 142 being schematically shown in FIG. 2 as a variable resistor). It should be noted that, in one other form, the switches 144, 146 and 148 can be eliminated and a potentiometer type of volume control can be utilized in lieu thereof, the volume of the feedback signals supplied to the summing amplifier 72 being controllable from approximately zero to a maximum level via the variable resistor or potentiometer.

The oscillator network 244 is, more particularly, a fixed frequency, constant amplitude, sinusoidal resistance-capacitance coupled type of oscillator network, and the switching transistor 240, more particularly, is constructed such that the feedback control signals 120, 122 and 124 saturate the switching transistor 240 connected thereto, thereby biasing the switching transistor 240 in the "on" position allowing current flow through the switching transistor 240 to ground and activating the oscillator network 244. In the "on" position of the on-off controls 144, 146 and 148, the feedback oscillator output signals 132, 134 and 136 are each connected to the input of the summing amplifier 72, as diagrammatically shown in FIG. 2.

The summing amplifier 72 and the output indicator 76 of the bio-feedback apparatus 10a is shown in more detail in FIG. 6. The feedback oscillator output signals 132, 134 and 136 are each connected to one of the inputs of the summing amplifier 72 via resistors 278, one resistor 278 being interposed between the summing amplifier 72 and each feedback oscillator output signal 132, 134 and 136, respectively. The other input of the summing amplifier 72 is connected to ground, the summing amplifier 72 thereby providing an amplifier of the type generally referred to as a "summing" or "mixer" type of amplifier. A feedback loop is provided around the summing amplifier 72, generally between the output of the summing amplifier 72 and the signal input to the summing amplifier 72, and a resistor 280 is interposed in the feedback loop.

The output of the summing amplifier 72 is connected to the primary side of a transformer 282 and the secondary side of the transformer 282 is connected to a speaker 284 and a headset 286. A switch 288 is interposed between the transformer 282 and the speaker 284, the switch 288 connecting the speaker 284 to the output of the summing amplifier 72 in the closed position thereof and disconnecting the speaker 284 from the output of the summing amplifier 72 in the open position thereof.

The summing amplifier 72 thus receives the feedback oscillator output signals 132, 134 and 136 and provides an output signal indicative of the signal mix thereof, the summing amplifier output signal being transformer coupled to the speaker 284 and the headset 286 for providing a subject-perceivable auditory type of feedback, each feedback signal indicating the presence of a sensed signal within the preset frequency ranges of one of the processing channels 78, 80 and 82. As mentioned before, the oscillator output signals 132, 134 and 136 each have a preselected frequency such that the separate tones being simultaneously amplified and produced via the summing amplifier 72 are distinguished by the subject or, in other words, such that when two or more oscillator output signal tones are bieng produced simultaneously by two or more of the feedback processing channels 78, 80 and 82, the simultaneously produced feedback oscillator output signals 132, 134 and 136 are individually identifiable and distinguishable by the subject. It should also be noted that the output indicator 76 can include other forms of audio feedback, and can also be constructed to produce various forms of visual feedback indications. In any event, the subject-perceivable feedback produced during the operation of the bio-feedback apparatus 10a is indicative of a signal presence in one of the processing channels 78, 80 and 82 wherein the signal has a minimum preset amplitude and is of a minimum predetermined duration.

Description of FIGS. 10 through 31

Shown in FIGS. 10 through 31 is a bio-feedback apparatus 10b, constructed similar to the bio-feedback apparatus 10 and 10a, described before, to sense and detect brain-waves or varying potentials produced by the subject and to process predetermined, preselected portions of the varying potential through separate processing channels to produce sugject-perceivable feedback indications indicative of various parameters related to the presence of a predetermined, identifiable signal component portion of the detected and sensed brain-wave potential from the subject. The bio-feedback apparatus 10b includes a brain-wave indicator 30b, constructed similar to the brain-wave indicator 30a of FIG. 2, the brain-wave indicator 30b including: a reference electrode 310 attached to the subject and providing an output signal 312; a right electrode 314 connected to the subject and providing an output signal 316; and a left electrode 318 connected to the subject and providing an output signal 320.

The electrodes 310, 314 and 318 are constructed and attached to the subject in a manner similar to that described before with respect to the electrodes 38, 42 and 46 of the bio-feedback apparatus 10a, shown in FIG. 2. In one operational embodiment, the right electrode 314 is, more particularly, attached to a preselected scalp site generally on the right side of the subject's head (preferably at or near the occipital area on the right side of the individual's head), and the left electrode 318 is attached to a preselected scalp site generally on the left side of the sugject's head (preferably at or near the occipital area on the left side of the subject's head). In one form, the subject's left earlobe and right earlobe are tied together, the common tie being utilized as a reference for monopolar recording of the brain-wave signals produced by the subject. This latter electrode attachment is preferably effected by rubbing in a salt paste or the like and subsequently attaching an earclip electrode, preferably filled with a salt paste or the like to each of the subject's ears. The reference electrode 310 provides the ground or neutral electrode and is, in one form, a plate type electrode attached to the subject's left wrist, for example. In any event, the reference electrode 310, the right electrode 314, and the left electrode 318 are each attached to the subject to sense and detect the varying potential produced by the subject's brain and to provide output signals 312, 316 and 320, indicative of the detected, sensed varying potential of the individual's brain and, more particularly, to provide output indications indicative of the varying potential produced by the individual's brain at two separate, distinct positions.

The separately detected brain-wave potentials are sensed simultaneously by the brain-wave indicator 30b, and the electrode output signals 312, 316 and 320 indicative of the two separately sensed varying potentials, sometimes referred to herein as the left and the right channels, are simultaneously connected to the input of a signal input controller 322, the signal input controller 322 receiving, amplifying and equalizing the amplitudes of the received signals and providing amplified, amplitude equalized output signals 324 and 326. The output signal 324 is, more particularly, provided in response to the received input signals from the left side of the subject's brain (the left channel), and the output signal 326 is, more particularly, provided in response to the received signals from the right side of the subject's brain (the right channel). It should be particularly understood that the terms "left" and "right" are utilized above and below to designate separate sensing sites on the subject and to distinguish separate controlling channels of the bio-feedback apparatus 10b merely for the purpose of reference and signal or channel identification.

The signal input controller 322 also provides an output signal 328 responsive to the received input signals from the brain-wave indicator 30b, the signal input controller output signal 328 being connected to and received by a permanent recorder indicator 330. The permanent recorder indicator 330 is, in a preferred form, of the chart driven polygraph type recorder constructed to receive input signals and to provide a permanent chart type feedback indicative of preselected parameters of an input signal connected thereto, such recorder indicators being well known in the art and commercially available from such manufacturers as, for example, Beckman Instruments of Chicago, Illinois. More particularly, and with respect to the signal input controller output signal 328, the permanent recorder indicator 330 provides a permanent chart-type output indicative of the detected sensed brain-wave potential from the two preselected scalp sites.

The signal input controller output signals 324 and 326 are connected to a left-right select switch 332, as shown in FIG. 10. The left-right select switch 332 receives the signal input controller output signals 324 and 326 and provides an output signal 333. In one position, the left-right select switch 332 selectively and switchingly connects one of the signals 324 and 326 to the feedback signal controller 334 via the signal 333; and, in one other position, the left-right select switch 332 selectively and switchingly connects both of the signals 324 and 326 to the feedback signal controller 334 via the signal 333. The left-right select switch 332, in a preferred form, includes switching components in various portions of the bio-feedback apparatus 10b to provide complete flexibility in controlling the permanent, the visual, and the audio feedback, as will be made more apparent below.

The feedback signal controller 334 is constructed to selectively separate the controlling channels 324 and 326 into separate processing channels, each processing channel receiving and processing a predetermined component or portion of the controlling channels 324 and 326, in a manner somewhat similar to that described before with respect to the bio-feedback apparatus 10a, shown in FIG. 2. In one preferred form, the feedback signal controller 334 includes eight processing channels, four of the processing channels being connected to the controlling channel 324, and the remaining four processing channels being connected to the controlling channel 326. The band width of each of the four processing channels connected to one of the controlling channels 324 or 326, more particularly, corresponds with preselected, identifiable, frequency components of the varying potential sensed and detected from the subject. The four processing channels connected to the controlling signal 324 and the four processing channels connected to the controlling signal 326, each include: one channel for processing received signals within a frequency band of 0.5 Hz. to 4.0 Hz., referred to as the Delta frequency band; one channel for processing received signals within a frequency band of approximately 4.0 Hz. to 8.0 Hz., referred to as the Theta frequency band; one channel for processing received signals within a frequency band of approximately 8.0 Hz. to 13.0 Hz., referred to as the Alpha frequency band; and one channel for processing received signals within a frequency band of approximately 13.0 Hz. to 26.0 Hz., referred to as the Beta frequency band.

The feedback signal controller 334 provides output signals 336, 338, 340 and 341, each output signal being indicative of the signal presence within the four processing channels of the controlling channel 324 or 326. More particularly, the feedback signal controller output signal 336 is indicative of signal presence within any of the processing channels of the left controlling signal 324; the feedback signal controller output signal 341 is indicative of signal presence within any of the processing channels of the right controller signal 326; and the signal controller output signals 338 and 340 are indicative of signal presence within any of the processing channels of the preselected controlling channel 324 or 326, in one form, the output signals 338 and 340 being indicative of signal presence within any of the processing channels of each controlling channel 324 and 326, in one other form, in a manner and for reasons which will be made more apparent below.

The feedback signal controller output signal 336 is connected to an audio signal controller 338 providing an audio output control signal 340 for activating an audio output indicator 342, the audio output indicator 342 providing a subject-perceivable, audio type of feedback indicative of signal presence within the processing channels of the controlling channel 324 in response to the received output signal 336. The feedback signal controller output signal 338 is connected to one of the channels of the permanent recorder indicator 330, the permanent recorder indicator 330 receiving the feedback signal controller output signal 338 and providing a chart-type permanent output indication indicative of signal presence within the processing channels of the controlling channels 324 and 326 in response to the received output signal 338.

The feedback signal controller output signal 340 is connected to a data reduction controller 344, the data reduction controller 334 providing an output signal 346 in response to the received output signal 340. The data reduction controller 344 is, more particularly, constructed to provide the output signal 346 indicative of the percentage of time during a subsequent predetermined epoch of time wherein a signal presence existed in the four processing channels of the controlling channels 324 and 326.

The feedback signal controller output signal 338 and the data reduction controller output signal 346 are each connected to a visual output controller 348, the visual output controller receiving the output signals 338 and 346 and providing a visual output control signal 350 in response thereto. The visual output control signal 350 is connected to a visual output indicator 352 providing a subject-perceivable, visual feedback indication of the received signals 338 and 346, thereby being indicative of signal presence and the percentage of time during a subsequent, predetermined epoch of time wherein a signal existed in the four processing channels of the controlling channel 324 and 326.

The feedback signal controller output signal 341 is connected to an audio output controller 354, the audio output controller 354 receiving the output signal 341 and providing an audio controller output signal 356 in response thereto. The audio controller output signal 356 is connected to and received by an audio output indicator 358, the audio output indicator 358 providing subject-perceivable output feedback indications indicative of signal presence in any of the four processing channels of the controlling channel 326. It should also be noted that, in a preferred form, the audio output indicators 342 and 358 are each connected to provide a stereo and a mono mode or form of audible feedback during the operation of the bio-feedback apparatus 10b, in a manner which will be described in greater detail below.

In general, the bio-feedback apparatus 10b receives and processes two separate, distinct controlling channels 324 and 326 (sometimes referred to herein as the left controlling channel 324 and the right controlling channel 326), each controlling channel 324 and 326 being responsive to and indicative of distinct, separate potentials sensed and detected at different scalp sites on the subject. The signal input controller 322, the left-right select switch 332, the feedback signal controller 334 and the data reduction controller 344 are each constructed to receive and process the controlling channels via a plurality of processing channels to provide selectively controlled feedback indications indicative of a plurality of combinations of the controlling channels 324 and 326, and the processing channels therein, in a manner which will be made more apparent below.

One processing channel of the feedback signal controller 334 is diagrammatically shown in FIG. 11, and generally includes: a filter 360, a zero crossing detector 362, an amplitude discriminator 364, a comparator controller 366, an atuomatic gain controller 368, a tachometer network 370, a bandpass controller 372, a voltage controlled oscillator 374, and a signal converter 376, the audio output controller 338 or 354, the audio output indicator 342 or 358, the visual output controller 348, the visual output indicator 352, and the permanent recorder indicator 330 also being diagrammatically shown in FIG. 11 connected to receive signals from the single, diagrammatically illustrated processing channel of the feedback signal controller 334 for the purpose of clarity of description. It should be emphasized that the feedback signal controller 334 has, in a preferred form, eight processing channels (four processing channels connected to and associated with each controlling signal 324 and 326, respectively), as described before.

The filter 360 receives the amplitude equalized signal from the controlling channel 324 or 326 connected thereto and provides an output signal 380 in response thereto. In a preferred form, the filter 360 is an active bandpass filter constructed to selectively pass the frequency component of the received signal within the preselected passband of the filter 360 via the filter output signal 380. In one preferred form, each controlling channel 324 and 326 includes four filters 360, each filter 360 being constructed and sized to selectively separate the frequency components of the received signal such that the four processing channels of each controlling channel 324 and 326 selectively receive and process signals having predetermined frequencies within the Alpha, the Beta, the Theta and the Delta frequency bands, described before.

The filter output signal 380 is connected to the zero crossing detector 362 and to a portion of the amplitude discriminator 364. The zero crossing detector 362 provides an output signal 382 which is a control voltage indicative of the zero crossings of the filter output signal 380. More particularly, the zero crossing detector 362 provides an output control voltage signal 382 in a "low" state each time the filter output signal crosses zero in a positive going direction and an output control voltage signal 382 in a "high" state each time the filter output signal crosses zero in a negative going direction. The zero crossing detector output signal 382 is thus indicative of the time interval between changes of the filter output signal 380 relative to positive and negative going signals of the filter output signals 380.

The amplitude discriminator 364 receives the filter output signal and develops a control voltage output signal 384 proportional to the amplitude of a received filter output signal of a predetermined minimum amplitude level. The control voltage is held in the amplitude discriminator 364 and transferred to the amplitude discriminator output signal 384 in response to a received zero crossing detector output signal 382 in a "high" state, for reasons and in a manner to be described in greater detail below.

The comparator controller 366 receives the amplitude discriminator output signal 384 and is connected to the bandpass controller 372 via the signal path 386 therebetween for providing an output signal 387 indicative of signal presence in the particular processing channel associated therewith of a predetermined, minimum amplitude level and a predetermined, minimum signal duration. The comparator controller output signal 387 is connected to the audio output controller 338 or 354 for providing the subject-perceivable, audio output indications via the audio output indicator 342 or 358 and to the visual output controller 348 for providing subjectperceivable visual feedback indications via the visual output indicator 352, in a manner to be described in greater detail below.

The zero crossing detector output signal 382 is also connected to the tachometer network 370, the tachometer network 370 providing an output signal 388 linearly proportional to the frequency of the filter output signal 380 in response to the received zero crossing detector output signal 382. The tachometer network 370 is also constructed to provide an oscillating output signal 389 in response to the received zero crossing detector output signal 382, the oscillating output signal 389 being connected to the amplitude discriminator 364 and controllingly transferring the stored control voltage thereinto the amplitude discriminator output signal 384.

The tachometer network output signal 388, in a preferred form, is connected to the permanent recorder indicator 330 for providing a chart-type permanent feedback indicative of the frequency of the filter output signal 380, as shown in FIG. 11. The tachometer network output signal 388 is also connected to the voltage controlled oscillator 374 constructed to provide an oscillating output signal 390 in response to the received tachometer network output signal 388, the oscillating output signal 390 being indicative of a signal presence in the processing channel associated therewith, in a manner similar to that described before with respect to the oscillators 126, 128 and 130 of the bio-feedback apparatus 10a shown in FIG. 2.

In one form, the voltage controlled oscillator output signal 390 is triangularly shaped and, in this form diagrammatically shown in FIG. 11, the output signal 390 is connected to the signal converter 376. The signal converter 376 is constructed to provide an oscillating output signal 392 having a sine-wave type of shape in response to a received triangularly shaped voltage controlled oscillator output signal 390.

The oscillating output signal 392 is connected to the automatic gain control 368, the automatic gain control 368 automatically controlling the signal gain of the output signal 392 and connecting the voltage controlled oscillator output signal 390 to the audio output controller 338 or 354 via the output signal 394. The audio output controller 338 or 354 providing a subjectperceivable audio feedback indication via the audio output indicator 342 or 358 in response to the received voltage controlled oscillator output signal 390 via the signal converter 376, the automatic gain control 368 and the audio output controller 338 or 354.

A portion of the data reduction controller 344 for processing the four processing channels of one of the controlling channels 324 and 326 is diagrammatically shown in FIG. 12, and generally includes: an analog switch 420, a delay oscillator 422, a delay signal controller 424, an overvoltage controller 426, a counter controller 428, a clock pulse generator 430, counters 432, and a digital/analog converter 434. In one form, the bio-feedback apparatus 10b includes only one data reduction portion as diagrammatically shown in FIG. 12, and, in this form, only one of the controlling channels 324 and 326 is utilized to develop subject-perceivable feedback signals indicative of the percentage of time during a subsequent epoch of time wherein a signal presence existed in the sensed brain-wave potential of the selected controlling channel 324 or 326. The data reduction controller 344, in one other form, includes a parallel portion, similar to the portion shown in FIG. 12, and, in this form, each portion receives one of the four processing channels of one of the controlling channels 324 and 326 for developing subject-perceivable output feedback indications.

In either event, the analog switch 420 receives the comparator controller output signals 387 from each of the processing channels of one of the controlling channels 324 and 326 via the input signal path 436 and an input signal 438 from the delay oscillator 422, as shown in FIG. 12. The analog switch 420 is constructed to connect the delay oscillator output signal 438 to the delay signal controller 424 via the analog switch output signal 440 in response to a received signal 436 indicating signal presence in the processing channels of the controlling channel 324 or 326 connected to the analog switch 420.

The delay signal controller 424 includes a plurality of recording channels, each channel receiving and recording the delay oscillator output signal 438 via the signal path 440 when connected thereto via the analog switch 420. The analog switch 420, more particularly, connects the delay oscillator output signal 438 to one of the recording channels of the delay signal controller 424 in response to a received processing channel signal indicating signal presence, the delay signal controller 424 recording the received signals over a predetermined epoch of time. Each recording channel of the delay signal controller 424 records over a predetermined epoch of time, and the portion of each recording channel having the delay oscillator output signal 438 recorded thereon is indicative of the portion of time during the predetermined epoch of time when a signal presence existed on the processing channel associated therewith.

The recorded signals of the delay signal controller 424 are subsequently connected to the overvoltage controller 426 via the signal 442, the overvoltage controller 426 providing d-c control votlage signals via an overvoltage controller output signal 444 in response to the recorded delay oscillator output signals on the recording channels of the delay signal controller 424. The signal 436, the overvoltage controller output signal 444 and a clock pulse 446, generated via the clock pulse generator 430, are each connected to the counter controller 428, the counter controller 428 providing an output signal 448 responsive to the received overvoltage controller output signal 444. In a preferred form, the counter controller 428 also includes a portion receiving the comparator controller output signal and provides an output signal indicative of the average percentage of time during which a signal presence existed in a processing channel for an epoch of time, as will be described in greater detail below.

The counters 432, shown in FIG. 12, are, in a preferred form, of the type generally referred to in the art as a digital type up/down counter constructed to count up and down in response to received control signals, and providing output signals in response thereto, such as a synchronous binary up-down counter commercially available from such companies as Texas Instruments of Dallas, Texas. The counter controller output signal 448 includes the clock pulse 446, and an up-count and a down-count control signal for activating the counters 432 in the proper counter mode in response to the received overvoltage controller output signal 444.

The counters 432 are, in one form, connected to provide what is commonly referred to as an "8-bit" output signal 450, the count provided via the counter digital output signal 450 being a predetermined count, such as 1000, for example, in one operational embodiment and being determined on the general basis of a continuous count for the predetermined, controlled epoch of time. The count provided via the counter output signal 450 is digitally indicative of signal presence in the processing channels during the subsequent predetermined epoch of time. The counter controller output signal 450 is connected to the digital/analog converter 434 and the digital/analog converter 434 converts the digital counter output signal 450 to an analog voltage output signal 452 wherein the d-c level moves up (more positive) and down (more negative) in discrete steps responsive to the output count of the counters 432. The digital/analog output signal 452 is connected to the permanent recorder indicator 330 and to the visual output controller 348, as shown in FIG. 10 and described generally before. Assuming that each controlling channel 324 and 326 includes four processing channels, as described before, the overvoltage controller output signal 444, the counter controller output signal 448, the counter output signal 450, and the digital/analog converter output signal 452, each include a portion responsive to and indicative of one of the processing channels, the four processing channels being similarly processed in parallel through the data reduction controller 344.

SIGNAL INPUT CONTROLLER

A preferred embodiment of the signal input controller 322 is schematically shown in FIG. 13 and generally includes: a polygraph 510 and an amplitude equalizer 512. The electrode output signals 312, 316 and 320 are connected to the polygraph 510 and a portion of the polygraph 510 is connected to the amplitude equilizer 512, the amplitude equalizer 512 providing the controlling channel signals 324 and 326, described before with respect to FIG. 10.

The left electrode output signal 320 is connected to one input of a left preamplifier 514 and the other input of the left preamplifier 514 is connected to receive the reference electrode output signal 312. The right electrode output signal 316 is connected to one input of the right preamplifier 516 and the other input of the right preamplifier 516 is connected to receive the reference electrode output signal 312. The left and the right preamplifiers 514 and 516 provide the initial signal preamplification, the left preamplifier 514 providing an amplified output signal 518 and the right preamplifier 516 providing an amplified output signal 520.

The amplified output signal 518 is connected to one input of a left power amplifier 522 via a three-position switch 524, an amplified output signal 526 from the left power amplifier 522 being connected to one channel of a write-out indicator 528. The amplified output signal 520 is connected to one input of a right power amplifier 530 via a three-position switch 532, an amplified output signal 534 from the right power amplifier 530 being connected to one other channel of the write-out indicator 528.

In one form, the write-out indicator 528 is constructed to provide a graph-type permanent feedback indicative of and in response to received input signals 526 and 534 connected thereto, and constitutes a portion of the permanent recorder indicator 330 (shown in FIGS. 10 and 11). A polygraph constructed in a manner generally described above with respect to the polygraph 510 is commercially available from such companies as Beckman Instruments of Chicago, Illinois, for example, this type of instrument being constructed to receive and record EEG signals.

In the switch position of the switches 524 and 532, shown in FIG. 13, the left preamplifier 514 is connected directly to the left power amplifier 522 and the right preamplifier 516 is connected directly to the right power amplifier 530, the switches 524 and 532 being mechanically connected. The switches 524 and 532 have two other switch positions, the two other switch positions being designated in FIG. 13 via the letter references "L" and "R." In the L switch position of the switches 524 and 532, the left preamplifier 522 is connected directly to the write-out indicator 528 via the power amplifier 522, the right preamplifier output signal 520 being connected to ground. In the R switch position of the switches 524 and 532, the right preamplifier 516 is connected directly to the write-out indicator 528 via the power amplifier 530, the left preamplifier output signal 518 being connected to ground.

The left preamplifier output signal 518, generally between the left preamplifier 514 and the switch 524, is connected to the positive input of a left equalizer amplifier 536 via a coupling capacitor 538, and the right preamplifier output signal 520, generally between the right preamplifier 516 and the switch 532, is connected to the positive input of a right equalizer amplifier 540 via a coupling capacitor 542. The left equalizer amplifier 536 provides an output signal 544 connected to the left-right select switch 332 via a variable resistor 546, and the right equalizer amplifier provides an output signal 548 connected to the left-right select switch 332 via a variable resistor 550, the equalizer amplifier output signals 544 and 548 connected to the left-right select switch 332 via the variable resistors 546 and 550 being the signal input controller output signals 324 and 326 (shown in FIGS. 10 and 13).

The equalizer amplifiers 536 and 540 each include a feedback loop having a resistor 552 interposed therein, each feedback loop being connected to the amplifier output signal and the negative input of one of the equalizer amplifiers 536 and 540. A capacitor 554 and a resistor 556 are connected generally between the two inputs of each equalizer amplifier 536 and 540, and a resistor 548 is connected generally between each capacitor 554 and resistor 556 of the equalizer amplifiers 536 and 540 and to ground.

The equalizer amplifier output signals 324 and 326 are each connected to one of the inputs of the power amplifiers 522 and 530, generally opposite the inputs thereto connected to one of the preamplifiers 514 and 516, as shown in FIG. 13. The power amplifiers 522 and 530 of the polygraph 510 have switch selectable inputs thereto, and are connected to the write-out indicator 528 and to the variable resistors 546 and 550 such that the amplitude of the two input channels received by the signal input controller 322 can be adjusted to a position wherein the amplitudes are substantially equal, in a manner to be made more apparent below.

The amplitude equalizer 512 thus equalizes or balances the amplitudes of the left and the right preamplifiers output signals 518 and 520, respectively, or, more generally, equalizes and balances the amplitudes of the amplified signals detected and sensed by the left and the right electrodes 314 and 318. The equalizing and balancing of the signals detected and sensed via the electrodes 314 and 318 provides a standard or basic amplitude facilitating the design of the various components and assemblies of the bio-feedback apparatus 10b to provide the various feedback signals in a more efficient, more positive and controlled manner.

It should be noted that the potentials sensed and detected by the left and the right electrodes 314 and 318 will, in some instances, vary due to the inherent construction and various connections of the electrodes 314 and 318, including the attachment of the electrodes 314 and 318 to the subject, and, in some instances, subjects produce higher potentials on the left or the right side of the individual's head, thereby resulting in sensed detected potentials of an unbalanced or unequalized amplitude, thereby necessitating the equalizing of the reference or average amplitudes of the signals 324 and 326. The sensed, detected potentials from the subject will, of course, have amplitude variations and these subject-produced variations remain in the controlling channels signals 324 and 326, the controlling channel signals 324 and 326 merely being shifted or adjusted to vary about a standard, predetermined amplitude axis by adjusting the variable resistors 546 and 550 of the amplitude equalizer 512, the predetermined reference amplitude axis being, more particularly, defined by a predetermined voltage value.

FEEDBACK SIGNAL CONTROLLER

The selected controlling channel signals 324 and 326 are connected to the feedback signal controller 334 (diagrammatically shown in FIG. 10) via the left-right select switch 332, one portion of the feedback signal controller 334 being shown in FIG. 14 and basically including: a comparator drive 560, a comparator 562, a switch drive 564, a threshold adjust 566 and a switch network 568. One controlling channel signal 324 and 326 is connected to the positive input of a comparator drive amplifier 570 via a dc-blocking capacitor 572. A resistor 574 is connected in parallel with the controlling channel signal 324 or 326 input to the comparator drive amplifier 570, the resistor 574 being connected to a variable resistor 576.

The variable resistor 576 is connected on one side to a negative power supply (not shown) via a pin connection 578 and on the opposite side to a positive power supply (not shown) via a pin connection 580. A resistor 582 is interposed between the variable resistor 576 and the pin connection 578, and a resistor 584 is interposed between the variable resistor 576 and the pin connection 580. The variable resistor 576 adjustably set to control the d-c level of the input level of the input controlling signal 324 or 326 to the comparator drive amplifier 570, during the operation of the bio-feedback apparatus 10b.

The comparator drive amplifier 570 provides an amplified output signal 586 for driving a dual comparator 588. The comparator drive 560 also includes a feedback loop connected to the comparator drive amplifier output signal 586 and to the negative input of the comparator drive amplifier 570, a variable resistor 590 being interposed in the feedback loop. The variable resistor 590 provides a variable gain control for the comparator drive amplifier 570 for setting a predetermined voltage at which the dual comparator 588 will trip or change the state of the output signal therefrom to activate the switch network 568, in a manner to be described in greater detail.

A capacitor 592 and a resistor 594 are connected to the negative input of the comparator drive amplifier 570, generally between the variable resistor 590 and the comparator drive amplifier 570. The capacitor 592 and the resistor 594 are connected in parallel with the feedback loop and provide a filtering network for the feedback input signal to the comparator drive amplifier 570.

The comparator drive output signal 586 is connected in parallel to two comparator amplifiers 596 and 598, the comparator amplifiers 596 and 598 constituting the amplifier networks of the dual comparator 588. More particularly, the comparator drive amplifier output signal 570 is connected to the comparator amplifier 596 via a resistor 600 and the comparator drive amplifier output signal 570 is connected to the comparator amplifier 598 via a resistor 602.

The negative input of the comparator amplifier 596 is connected to a positive voltage power supply (not shown) via a pin connection 604 and the positive input of the comparator amplifier 598 is connected between the resistor 608 and ground via a resistor 609. The resistors 606 and 608 comprise a voltage divider network interposed between the positive power supply connection 604 and ground, the negative input to the comparator amplifier 596 being connected to the voltage divider network generally between the resistors 606 and 608. The output signals of the comparator amplifier 596 and the comparator amplifier 598 are connected together to provide a single, dual-comparator output signal 610, the dual-comparator output signal 610 being connected to the emitter of a switching transistor 611, for reasons to be made more apparent below.

The comparator amplifier 596 includes a feedback loop connected to the output signal and to the positive input thereof, a feedback resistor 613 being interposed in the feedback loop of the comparator amplifier 596. The comparator amplifier 598 also includes a feedback loop connected to the output signal and to the positive input of the comparator amplifier 598, a feedback resistor 612 being interposed in the feedback loop of the comparator amplifier 598. The feedback loop of the comparator amplifier 588 and the comparator amplifier 598 are each connected to a negative power supply (not shown) via a pin connection 614 and a voltage limiting resistor 616 is interposed between the feedback loops and the pin connections 614.

The comparator 562 is connected to operate as a dual-comparator or "window" comparator, the comparator 562 having a passband with an upper and a lower limit adjustably set to predetermined values such that the comparator output signal 10 remains in a "high" state when the comparator drive output signal 586 is outside or exceeds the window limits, and such that the comparator output signal 610 is turned-over or switched to a "low" state when the comparator drive output signal 586 is within the window limits of the comparator 562, thereby producing the comparator output signal 610 indicative of a received signal 586 within the window limits. The voltage divider network comprising the resistors 606 and 608 functions to set the upper limit, and the resistors 616 and 609 function to set the lower limit of the comparator 562. The variable gain of the comparator drive amplifier 560 facilitates the setting of the threshold level of the comparator 562. The feedback resistor 612 cooperates with the voltage limiting resistor 616 to form a voltage divider network to reduce any "chatter" in the comparator output signal 610 which may occur, in some instances, when the comparator drive output signal 586 is near the upper and the lower window limits of the comparator 562.

Since the comparator drive output signal 586 is an alternating current type of signal, the comparator 562 will operate to eliminate feedback when receiving signal "spikes" caused by muscle artifacts, twitches or the like, the comparator 562 detecting the high amplitude spike and switching the comparator output signal 610 to a "high" status. However, assuming the sensed, subject produced potential fed to the comparator drive 560 via the controlling channel signal 324 or 326 is such that the comparator drive output signal 586 is within the upper and the lower window limits of the comparator 562, the comparator output signal 610 will be switched to the "low" state for activating the switch drive 564 and the switch network 568, in a manner to be described in greater detail below.

The switch drive 564 basically includes the switching transistor 611 which is biased in the "off" position in a "high" state of the comparator output signal 610 and is biased in the "on" position when the comparator output signal 610 is in the "low" position. The base of the switching transistor 611 is connected to ground via a resistor 618, and the collector of the switching transistor 611 is connected to a positive power supply (not shown) via a pin connection 620. A resistor 622 is interposed between the collector of the switching transistor 611 and the pin connection 620, and a resistor 624 is connected on one end thereof generally between the pin connection 620 and the resistor 622 and on the opposite end thereof to the base of the switching transistor 611, generally between the resistor 618 and the switching transistor 611.

The switch drive output signal is taken between the collector and ground of the switching transistor 611 via a conductor 626 and a ground conductor 628. The switch drive output signal 626 is connected through a diode 630 to a timing network 631 having a capacitor 632 connected in parallel with a variable resistor 634, the diode 630 and the timing network 631 comprising the threshold adjust 566. The time constant of the timing network 631 (determined by the values of the capacitor 632 and the variable resistor 634) is preset to a predetermined value such that the switch drive output signal 626 must exist or be present for a predetermined, controlled period of time subsequent to an output signal 636 being produced via the threshold adjust 566, and such that the switch drive output signal 624 must be terminated or cease to exist for a predetermined, controlled period of time prior to terminating the threshold adjust output signal 636, thereby assuring that the feedback provided via the bio-feedback apparatus 10b will be initiated and terminated in response to a received, sensed potential having a minimum signal duration. In a preferred form, the discharge time constant is relatively longer than the charge time constant of the timing network 631 when the diode 630 is reversed biased, thereby producing a relatively fast "turn-on" time and a relatively longer "turn-off" time to hold the FET switches 638 and 640 until the artifact has subsided and a relatively normal signal has returned.

The threshold adjust output signal 636 is connected in parallel to the gate of each of two FET switches 638 and 640 via a voltage limiting resistor 642. A capacitor 644 is connected between the source and the gate of each of the FET switches 638 and 640. The output signal 646 of the FET switch 638 is connected to the left filters and the output signal 648 of the FET switch 640 is connected to the right filters, as indicated in FIG. 14.

Thus, when a sensed subject-produced potential is received by the bio-feedback apparatus 10b and the controlling channel signals 324 and 326 received by the comparator drive 560 are of a minimum duration, controlled by the timing network 631, and within the upper and the lower window limits of the comparator 562, the switching transistor 611 is biased to the "on" position and the threshold adjust output signal 636 biases the gates of the FET switches 638 and 640 to the open position, thereby providing an output signal connected in parallel to the filters in each of the four processing channels in each of the controlling channels of the bio-feedback apparatus 10b.

Zero Crossing Detector

Shown in FIG. 15 is a typical zero crossing detector 362, one of the zero crossing detectors 362 being incorporated in each of the processing channels of the bio-feedback apparatus 10b. Each zero crossing detector 362 receives the filter output signal from one of the filters connected in one of the processing channels via a pin connection 660, the filter output signal being connected to the base of a first transistor amplifier 662 via a resistor 664 and a capacitor 666 being connected to the base of the first transistor amplifier 662 generally between the resistor 664 and the first transistor amplifier 662, as shown in FIG. 15. The collector of the transistor amplifier 662 is connected to a negative power supply (not shown) via a pin connection 668 and the emitter of the first transistor amplifier 662 is connected to a positive power supply (not shown) via a pin connection 670.

The zero crossing detector 362 also includes a second transistor amplifier 672, the collector of the second transistor amplifier 672 being connected to the negative power supply (not shown) via a common connection with the collector of the first transistor amplifier 662 to the pin connection 668. The emitter of the second transistor amplifier 672 is connected to a positive power supply (not shown) via a common connection with the emitter of the first transistor amplifier 662 to the pin connection 670. A resistor 674 is interposed between the emitter of the first transistor amplifier 662 and the pin connection 670, and a resistor 676 is interposed between the emitter of the second transistor amplifier 672 and the pin connection 670.

The emitter of the transistor amplifier 662 is connected to the negative input of a single comparator 678, generally between the transistor amplifier 662 and the resistor 674, and the emitter of the second transistor amplifier 672 is connected to the positive input of the single comparator 678, generally between the second transistor amplifier 672 and the resistor 676. The transistor amplifiers 662 and 672 are each high gain type of amplifiers and are each connected in the emitter-follower form, as shown in FIG. 15, to provide an impedance matching network between the filter output signals and the single comparator 678, the comparator 678 being a generally low input impedance device and the impedance matching network being thus sized and connected to produce a high input impedance input signal to the single comparator amplifier 678.

The single comparator amplifier 678 provides an output control voltage signal 679 at a pin connection 680, the single comparator amplifier 678 producing the control voltage signal 679 at the zero crossings of the input signal to the zero crossing detector 362; that is, the filter output signal connected to the pin connection 660 of the zero crossing detector 362. The output signal 679 of the single comparator amplifier 678 is normally in the "low" state, the output signal 679 being switched to the "high" state each time the filter input signal to the zero crossing detector 362 passes through zero on a downward slope (negative going direction) and each time the filter input signal to the zero crossing detector passes through zero on an upward slope (positive going direction--the output signal 679 returning to the "low" state each time the filter input signal to the zero crossing detector passes through zero on the upward slope.)

The single comparator amplifier output signal 679 is connected to the base of the second transistor amplifier 672 via a resistor 682, and the base of the second transistor amplifier 672 is connected to ground via a resistor 684. A resistor 686 and a variable resistor 688 are connected in series to the base of the second transistor amplifier 672, the resistor 686 and the variable resistor 688 being connected in parallel with the resistor 684, as shown in FIG. 15. The variable resistor 688 is connected to a positive power supply (not shown) via a pin connection 690 and varyingly controls the base bias for the second transistor amplifier 672 or, in other words, controls the level at which the zero crossing detector single comparator amplifier 678 switches the state of the output signal 679 therefrom.

Thus, each zero crossing detector 362 is constructed to receive one of the alternating filter output signals at the pin connection 660 of the zero crossing detector 362 and to provide an output control voltage on each zero crossing of the filter output signal in a negative and in a position going direction via the single comparator amplifier output signal 679 of the pin connection 680. Assuming, for example, that the variable resistor 688 is preset such that the single comparator amplifier 678 will produce a change in the output signal 679 therefrom at 50 millivolt, then the single comparator amplifier output signal 679 will change states each time the filter output signal connected thereto via the pin connection 660 passes above zero in a positive going direction by 50 millivolts and each time the filter output signal passes through zero in a negative going direction by 50 millivolts. Thus, in this example, the zero crossing detector 362 has approximately a 100 millivolt range. This type of construction is preferred in lieu of a zero crossing detector set at exactly zero to substantially reduce "chattering" in the single comparator amplifier output signal 679 and to provide a substantially more stable control voltage at the output pin connection 680 of the zero crossing detector 362.

AMPLITUDE DISCRIMINATOR

A preferred embodiment of the amplitude discriminator 364, generally described before with respect to FIG. 11, is schematically shown in FIG. 16, one of the amplitude discriminators 364 being incorporated in each processing channel of the bio-feedback apparatus 10b. The amplitude discriminator 364 includes a discriminator amplifier 694, having the negative input thereto connected to receive one of the filter output signals via a pin connection 696, a variable resistor 698 being interposed generally between the pin connection 696 and the negative input to the discriminator amplifier 694. The positive input to the discriminator amplifier 694 is connected to a variable resistor 700 via a resistor 702, one end of the variable resistor 700 being connected to ground and the opposite end of the variable resistor 700 being connected to a positive power supply (not shown) via a pin connection 704.

The variable resistor 698 interposed between the filter output signal and the discriminator amplifier 694 provides a controllingly variable gain adjustment for the discriminator amplifier 694. The variable resistor 700 connected to the positive input of the discriminator amplifier 694 adjustingly controls the d-c offset of the discriminator amplifier 694 or, in other words, provides an adjustment for shifting a discriminator amplifier output signal 706 in a positive d-c direction to overcome to some degree the forward drop of a diode 708 connected to receive the discriminator amplifier output signal 706. In a preferred form, the variable resistor 700 is set to biasingly shift the discriminator amplifier output signal 706 in a positive direction to a position wherein a relatively small amount of current leaks through the diode 708 during the operation of the amplitude discriminator 364, thereby substantially reducing the d-c loss through the diode 708.

A feedback loop is connected between the negative input and the output signal of the discriminator amplifier 694 and a feedback resistor 710 is interposed in the feedback loop. The discriminator amplifier output signal 706 is connected to the source connection of a first FET switch 712 via the diode 708, the drain connection of the FET switch 712 being connected to the gate of a second FET switch 714. The gate of the first FET switch 712 is connected to a pin connection 716 via a resistor 718 and a capacitor 720, the output signal 389 of the tachometer network 370 (shown in FIG. 11) being connected to the gate of the second FET switch 714 via the pin connection 716, for reasons and in a manner which will be made more apparent below.

The cathode of the diode 708 is normally non-conducting and essentially operates as an open switch in the amplitude discriminator 364. Thus, a filter output signal received at the pin connection 696 will be shifted in a positive d-c direction an amount determined by the setting of the variable resistor 700, the received filter output signal being amplified by the discriminator amplifier 694 and the output signal 706 being passed through the diode 708 to charge a capacitor 722, connected in parallel with the discriminator amplifier output signal 706, generally between the diode 708 and the first FET switch 712. It should be noted that the diode 708 is constructed to conduct only when the received filter signal input thereto from the discriminator amplifier 694 is going in a positive direction and thus, when the received filter signal begins to swing in a negative going direction, the diode will be reversed biased and the charge will be held on the capacitor 722, for reasons which will be made more apparent below.

The collector of a switching transistor 724 is connected to the discriminator output signal 706, generally between the diode 708 and the capacitor 722, the switching transistor 724 being connected in parallel with the capacitor 722. The emitter of the switching transistor 724 is connected to ground via a common connection with the ground side of the capacitor 722. The base of the switching transistor 724 is connected to receive the output signal from the zero crossing detector 362 via a pin connection 726, a capacitor 728 and a resistor 730 being interposed generally between the switching transistor 724 and the pin connection 726. A resistor 732 and a diode 734 are each connected in parallel and connected to the base of the switching transistor 724 in parallel with the zero crossing detector input signal thereto via the pin connection 726.

Thus, as the filter output signal crosses through the preset trigger or zero level of the zero crossing detector 362 in a negative going direction, the diode 708 is reversed biased and the zero crossing detector 362 will provide output signal in a high state at the pin connection 726 biasing the switching transistor 724 in the "on" position momentarily by differentiating the positive going edge of the output signal from the zero crossing detector 362 via the network comprising the capacitor 728 and the resistors 730 and 732, and discharging the capacitor 722 to ground. The diode 708 is forward biased by the inverting amplifier 694 and charges the capacitor 722 to the peak amplitude of the negative going wave from the filter output. As the filter output signal crosses through the preset trigger or zero level of the zero crossing detector 362 in a positive going direction, the output signal of the zero crossing detector 362 changes to the low state. A negative pulse is generated by differentiating the high to low state change of the zero crossing detector 362 via the network comprising the capacitor 728 and the resistors 730 and 732. This produced pulse is shunted to ground via the diode 734 thereby preventing the reverse bias from breaking down the base emitter junction of the switching transistor 724. The switching transistor 724 remains in the "off" position, the positive going filter output signal providing a reverse bias on the diode 708 via the discriminator output signal 706. The capacitor 722 is thus continuously charged and discharged in response to a positive and negative going filter output signal during the operation of the bio-feedback apparatus 10b. The capacitor 722 will be charged to a new level each time the discriminator amplifier output signal 706 goes positive, assuming the capacitor 722 has been subsequently discharged.

The amplitude discriminator 364 includes a memory capacitor 736 which is connected in parallel to the drain of the first FET switch 712 and the gate of the second FET switch 714. The drain connection of the second FET switch 714 is connected to a positive power supply (not shown) via a pin connection 738 and the source connection of the second FET switch 714 is connected to a negative power supply (not shown) via a pin connection 740. A resistor 742 is interposed between the source connection of the second FET switch 714 and the pin connection 740. An output signal 746 of the amplitude discriminator 364 is connected to the source side of the second FET switch 714, generally between the second FET switch 714 and the resistor 742, as shown in FIG. 16.

The pin connection 716 or, in other words, the gate of the first FET switch 712 is connected to receive an output signal from a multi-vibrator connector in the tachometer network 370, described generally before the respect to FIG. 11 and to be described in greater detail below. The first FET switch 712 operates to transfer the charge on the capactor 722 to the memory capacitor 736 when the input signal to the gate of the first FET switch via the pin connection 716 biases the first FET switch in the "open" position, thereby essentially connecting the capacitors 722 and 736 in a parallel and transferring the charge from the capacitor 722 to the memory cpacitor 736. The FET switch 712 is biased to the non-conducting state by a resistor 744 which is connected to a negative power supply (not shown) at the pin connection 704 and a resistor 741 connected to groud, the junction of the resistors 744 and 741 is connected to the junction of the capacitor 720 and the resistor 718 connected in series between the pin connection 716 and the gate of the FET switch 712. In a preferred form, the capacitor 722 is relatively larger than the capacitor 736, and thus a charge will remain on the capacitor 722 after the transfer of the charge to the memory capactor 736, thereby necessitating the discharging of the capacitor 722 after the transferring of the charge therefrom to the memory capacitor 736 to position the capacitor 722 to receive the next charging signal produced via the discriminator amplifier output signal 706, during the operation of the bio-feedback apparatus 10b.

Thus, the first FET switch 712 of the amplitude discriminator 364 is opened and closed as controlled via the output signal of the multi-vibrator portion of the tachometer network 370 to transfer the charge of the capacitor 722 to the memory capacitor 736 after the capacitor 722 has been charged via the amplitude discrimination output signal 706 and before the discharging of the capacitor 722 in response to the zero crossing detector output signal. The charge transferred to the memory capacitor 736 feeds the gate of the second FET switch 714 which is a high impedance device. Thus, the second FET switch 714 will not drain the charge from the memory capacitor 736 and the second FET switch 714 is thus utilized in the amplitude discriminator 364 as a source follower or, in other words, a high input impedance -- low output impedance device.

Thus, the amplitude discriminator output signal 746 is a control voltage (d-c) proportional to the charge on the memory capacitor 736. The amplitude discriminator 364 is thus essentially a positive peak reading memory circuit, the peak amplitude of each cycle of the amplitude discriminator output signal 706 being transferred to the memory capacitor 736 via a multi-vibrator output signal generated by a positive going zero crossing filter output signal.

COMPARATOR CONTROLLER

The amplitude discriminator output signal 746 is connected to the comparator controller 366, as shown in FIG. 16 and, more particularly is connected to the negative input of a first comparator 750 via a resistor 752. The positive input and the feedback loop of the first comparator 750 is connected to a resistor 754. The first comparator 750 provides an output signal 756 therefrom which is normally in the "high" state, the first comparator 750 being constructed to change the first comparator signal 756 to a "low" state in response to a received amplitude discriminator output signal 746 exceeding a predetermined threshold level setting of the first comparator 750.

The first comparator 750 includes a feedback loop connected between the output signal 756 and the positive input thereto, a feedback resistor 758 being interposed in the feedback loop. A variable resistor 760 is connected to the positive input of the first comparator 750, generally between the resistor 754 and the first comparator 750 to controllingly adjust the minimum threshold amplitude level of the first comparator 750. A resistor 762 is connected in series to the variable resistor 760, and is connected to a positive power supply (not shown) via a pin connection 764.

The comparator controller 366 also includes a second comparator 768 having an output signal 770, the second comparator 768 being constructed such that the second comparator output signal 770 is normally in the "low" state and such that, when an input signal having a predetermined amplitude level is applied to the negative input of the comparator 768, the second comparator 768 will change the state of the second comparator output signal 770 to a "high" state. The positive input of the second comparator 768 is connected to a variable resistor 772 to controllingly adjust the minimum threshold amplitude level of the second comparator 768. The variable resistor 772 is connected in series with a resistor 774 to a negative power supply (not shown) via a pin connection 776. The side of the variable resistor 772, opposite the side thereof connected to the negative power supply, is connected to a positive power supply at the pin connection 764 via a resistor 778.

The first comparator output signal 756 is connected to a portion of the bandpass controller 372, the bandpass controller 372 providing a bandpass controller output signal 780 connected to the negative input of the second comparator 768 via a resistor 782. A capacitor 784 is connected in parallel with the negative input of the second comparator 768, generally between the second comparator 768 and the resistor 782. The output signals 756 and 780 between the comparator controller 366 and the bandpass controller 372 constituting a portion of the signal path 386, shown in FIG. 11 and generally described before.

When the first comparator 750 receives an incoming signal to the negative input thereto via the amplitude discriminator output signal 746 which exceeds the preset threshold level of the first comparator 750, the state of the first comparator output signal 756 will change to the "low" state and, assuming the bandpass controller output signal 780 is initiated in response to a received first comparator output signal 756 in the "low" state, the capacitor 784 will begin to discharge at a charge rate determined by the values of the capacitor 784 and the resistor 782. The capacitor 784 will, of course, be discharged at an exponential rate and, when the charge on the capacitor 784 reaches the preset threshold level of the second comparator 768 (determined by the setting of the variable resistor 772), the second comparator 768 will change the state of the second comparator output signal 770 to provide a second comparator output signal 770 in a "high" state at the output pin connection 786.

A variable resistor 788 and a resistor 789 are connected between the second comparator output signal 770 and the positive input of the second comparator 768. A negative power supply (not shown) is connected to a pin connection 790 and to the junction between the resistor 789 and the second comparator output signal 770.

Thus, the comparator controller 366 is constructed such that when the d-c amplitude level of the amplitude discriminator output signal 746 exceeds the predetermined threshold level setting of the first comparator 750 for a sufficient period of time to discharge the capacitor 784 to an amplitude level exceeding the threshold level setting of the second comparator 768, the comparator controller 366 will provide an output signal 770 at the output pin connection 786 in the "high" state. In one operational example, the charge time or time constant determined by the resistor 782 and the capacitor 784 and the threshold level setting of the first comparator 750 via the variable resistor 760 is set such that the comparator controller 366 requires an incoming signal or, in other words, an amplitude discriminator output signal 746 having a duration equivalent to at least three cycles at the center band frequency, prior to activating the comparator controller output signal 770 in the "high" state. Further and considering the same operational example, in the Alpha band where the frequency range is from approximately 8.0 Hz. to 13.0 Hz., as mentioned before, the center band frequency is approximately 10.5 Hz. and thus the second comparator 768 of the comparator controller 366 will not change the state of the second comparator output signal 770 until the first comparator 750 has received an input signal above the threshold level setting determined by the variable resistor 760 for a period of time it takes for three cycles at 10.5 Hz. to pass through the first comparator 750 discharging the capacitor 784.

In this manner, the feedback generated by the biofeedback apparatus 10b is controlled such that a sensed, detected potential must produce an amplitude discriminator output signal 746 which exceeds the threshold level setting of the first comparator 750 and is of a sufficient duration to activate the second comparator 768 to change the state of the second comparator output signal 770 before feedback signals are initiated. The comparator controller output signal 770 at the pin 786 is a d-c control voltage of a predetermined amplitude level and is utilized to control the feedback signal of the bio-feedback apparatus 10b, in a manner to be described in greater detail below.

AUTOMATIC GAIN CONTROL

The automatic gain control 368, shown diagrammatically in FIG. 11 and shown in more detail in FIG. 16, is constructed to automatically control the amplitude of the feedback signal provided by the bio-feedback apparatus 10b, the automatic gain control 368 having an output signal provided at a pin connection 800 and receiving a signal from the voltage controlled oscillator 374 via the pin connection 804, and being connected to a positive power supply (not shown) via pin connections 802 and 806. The automatic gain control 368 includes an FET switch 810 having the gate connected to the amplitude discriminator output signal 746 via a resistor 812. The source connection of the FET switch 810 is connected to the emitter of a transistor amplifier 814 via a capacitor 816, and the drain connection of the FET switch 810 is connected to a variable resistor 818, a capacitor 820 being connected to the drain of the FET switch 810 and to the ground side of the variable resistor 818, as shown in FIG. 16. The gate of a second FET switch 822 is connected to ground and the drain connection of the FET switch 822 is connected to the emitter of the transistor amplifier 814 in parallel with the first FET switch 810, the source of the second FET switch 822 being connected to ground via a resistor 824.

The base of the transistor amplifier 814 is connected to the voltage controlled oscillator 374 via the pin connection 804, a capacitor 826 being interposed between the transistor amplifier 814 and the pin connection 804. A resistor 828 is connected to the base of the transistor amplifier 814 and ground generally between the transistor amplifier 814 and the capacitor 826. Another resistor 830 is connected to the base of the transistor amplifier 814 and the positive power supply (not shown), generally between the transistor amplifier 814 and the capacitor 826. The collector of the transistor amplifier 814 is connected to a resistor 832, the output of the automatic gain control 368 at the pin connection 800 being connected generally between the resistor 832 and the collector of the transistor amplifier 814.

Each automatic gain control 368 receives the output signal from one of the voltage controlled oscillators 374 at the pin connection 804, the voltage controlled oscillator output signal being applied across the resistor 828 when the amplitude discriminator output signal 746 is in a "high" state and of a sufficient amplitude to bias the FET switches 810 and 822 "open."

During the operation of the bio-feedback apparatus 10b, the FET switch 810 operates in the nature of a variable resistor and the FET switch 822 operates in the nature of a constant current source of, in other words, a current bias for the transistor amplifier 814. The automatic gain control 368 receives the output from the voltage controlled oscillator 374 at the pin connection 804 and the output of the automatic gain control 368 is responsive to the input from the voltage controlled oscillator 374, the circuitry of the automatic gain control 368 functioning to provide a voltage controlled gain to control the volume or loudness of the signal at the output pin connection 800 as a function of the received control voltage provided via the amplitude discriminator output signal 746. Thus, the automatic gain control 368 utilizes a fixed level input provided via the voltage controlled oscillator 374 and the automatic gain control 368 controls the gain of the voltage controlled oscillator 374 through the automatic gain control 368 to the output pin connection 800 thereby controlling the volume of the feedback signal provided via the voltage controlled oscillator 374 as a function of the amplitude discriminator output signal 746.

The variable resistor 818 provides a bias adjust to control the range of the volume level of the voltage controlled oscillator signal provided at the output pin connection 800 of the automatic gain control 368.

TACHOMETER NETWORK

One embodiment of a typical tachometer network 370 of the bio-feedback apparatus 10b is schematically shown in FIG. 17, the tachometer network 370 providing an output signal at the pin connection 834 connected to the pin connection 716 (FIG. 16) of the amplitude discriminator 364 and receiving the zero crossing detector output signal 679 via the pin connection 836. The tachometer network 370 includes a pair of transistor amplifiers 838 and 840, the emitters of the transistor amplifiers 838 and 840 each being connected to a ground, and a diode 842 being interposed between the emitter of the transistor amplifier 840 and the ground connection thereof.

The base of the transistor amplifier 838 is connected to a diode 844, the diode 844 being connected to a resistor 846 and the zero crossing detector output signal 679 being connected to the base of the transistor amplifier 838, generally between the diode 844 and the resistor 846 via a capacitor 848 and a resistor 850. The base of the transistor amplifier 840 is connected to a capacitor 852, the capacitor 852 being connected to the collector of the transistor amplifier 838. The base of the transistor amplifier 840 is also connected to a resistor 854 and a variable resistor 856. A resistor 858 is connected to the variable resistor 856 and to the capacitor 852, as shown in FIG. 17, the variable resistor 856 and the resistor 858 each being connected to a negative power supply (not shown) via a pin connection 860. The base of the transistor amplifier 838 is connected to a resistor 862 which is connected to a positive power supply (not shown) via a pin connection 864, a resistor 866 being connected to the base of the transistor amplifier 838, generally between the resistor 862 and the transistor amplifier 838. The resistor 866 is also connected to the collector of the transistor amplifier 840, the connection between the resistor 866 and the collector of the transistor amplifier 840 being connected to the negative power supply (not shown) via the pin connection 860 and connected to a conductor 868 via a resistor 870.

The conductor 868 is connected to the positive power supply (not shown) via the pin connection 864 and a resistor 872 is interposed in the conductor 868, generally between the connection of the resistor 870 to the conductor 868 and the pin connection 864. The conductor 868 is also connected to ground via a capacitor 874, the capacitor 874 being interposed in the conductor 868 generally between the connection of the resistor 870 to the conductor 868 and the ground connection thereof.

It will be apparent from the foregoing that the transistor amplifiers 838 and 840 are interconnected via the various components to provide a monostable multi-vibrator 876, the monostable multi-vibrator 876 being biased in the "on" (activated) and "off" (deactivated) state via the signal input thereto from the zero crossing detector 362. The diode 844 is positioned to cooperate with the "PNP" transistor amplifier 838 to require a negative going signal to trigger the monostable multi-vibrator 876 in the "on" position, the monostable multi-vibrator 876 being thus triggered in the "on" position in response to a received zero crossing detector output signal 679 in the "low" state. In the triggered "on" position of the monostable multi-vibrator 876, the output of the monostable multi-vibrator 876 is connected to and drives a switching transistor 880 or, in other words, the output of the monostable multi-vibrator 876 will turn the switching transistor 880 to the "on" position, since the base of the switching transistor 880 is connected to receive the output signal of the monostable multi-vibrator 876, for reasons which will be made more apparent below.

The emitter of the switching transistor 880 is connected to ground via a resistor 882, and is connected to the positive power supply (not shown) via a resistor 884. The collector of the switching transistor 880 is connected to function generator 886, the function generator 886 also being connected to the negative power supply (not shown) via the pin connection 860. The collector of the switching transistor 880 is also connected to the collector of the switching transistor 887, the collector of the switching transistor 887 also being connected to the function generator 886.

The output signal of the monostable multi-vibrator 876 is also connected to the base of a switching transistor 888 via a resistor 890, the collector of the switching transistor 888 being connected to the negative power supply (not shown) at the pin connection 860 and to the function generator 886. The emitter of the switching transistor 888 is connected to ground via a resistor 892, and the primary side of a transformer 894 is connected to the emitter of the switching transistor 888 via a capacitor 896, the capacitor 896 being connected, generally between the switching transistor 888 and the resistor 892. A resistor 898 is connected in parallel across the primary side of the transformer 894, generally between the capacitor 896 and the primary side of the transformer 894. The secondary side of the transformer 894 is connected to the base of the switching transistor 887 and to a common connection between the emitter of the switching transistor 887 and the emitter of a switching transistor 900, the base of the switching transistor 900 being connected to the base of the switching transistor 887 via a conductor 902, generally between the switching transistor 887 and the secondary of the transformer 894. The collector of the switching transistor 900 is connected to the gate of an FET switch 904, the common connection between the collector of the switching transistor 900 and the gate of the FET switch 904 being connected to the positive power supply (not shown) via a capacitor 906, as shown in FIG. 17.

The positive power supply (not shown) is connected to the emitter of a transistor amplifier 908 via a resistor 910, the base of the transistor amplifier 908 being connected to the FET switch 904 via a diode 912. The collector of the transistor amplifier 908 is connected to the FET switch 904 and to a negative power supply (not shown) via a pin connection 914. The output of the tachometer network 370 is taken at a pin connection 916 generally between the resistor 910 and the emitter of the transistor amplifier 908.

The function generator 886 is particularly constructed to cooperate with the tachometer network 370 within the frequency bands mentioned before with respect to the Alpha, the Beta, the Theta and the Delta frequency bands. A preferred embodiment of one function generator 886a constructed to operate within the frequency range of approximately 4.0 Hz. to approximately 26.0 Hz. is schematically shown in FIG. 18, and one preferred embodiment of a function generator 886b constructed to operate within frequency range of approximately 0.5 Hz. to approximately 4.0 Hz.

Referring more particularly to the embodiment of the function generator 886a (shown in FIG. 18), the function generator 886a includes an input pin connection 920 which is connected to the collectors of the switching transistors 880 and 887, as shown in FIG. 17. The input pin connection 920 is connected to a variable resistor 922 via a diode 924, a resistor 926 and a variable resistor 928 being interposed generally between the diode 924 and the variable resistor 922. The variable resistor 922 is connected to ground on one side thereof via a resistor 920 and to a negative power supply (not shown) at a pin connection 929 via a resistor 932.

One side of a capacitor 934 is connected to the input signal generally between the input pin connection 920 and the diode 924, the opposite side of the capacitor 934 being connected to the negative power supply (not shown) via the pin connection 929. A resistor 936 and a variable resistor 938 are connected in series and are connected in parallel with the capacitor 934.

When the monostable multi-vibrator 876 is triggered or activated in the "on" position for a predetermined time by the trigger input provided via the zero crossing detector output signal 679, the capacitor 934 is charged to the value of the negative power supply (not shown) connected thereto via the pin connection 929, the switching transistor 880 being subsequently biased to the "off" position. The resistor 936 and the variable resistor 938 connected in parallel with the capacitor 934 will provide a resistive bleed path for the capacitor 934, thereby discharging the capacitor 934 therethrough. In a preferred form, the capacitor 934 and the resistors 936 and 938 are sized to provide a relatively low time constant, the potential developed across the resistors 936 and 938 by the discharging of the capacitor 934 being essentially in the form of an exponentially shaped signal or wave. The variable resistor 938 thus allows the time constant to be adjustingly set to control the slope of the exponentially shaped discharge curve of the capacitor 934, for reasons which will be made more apparent below.

The positive side of the capacitor 934 is connected to the diode 924, and the diode 924 will thus conduct when the anode thereof is positive with respect to the resistive biasing network essentially consisting of the resistors and the variable resistors 922, 926, 928, 936 and 938. The bias network, includes two adjustable variable resistors, the variable resistor 928 adjustably setting the high time constant and the variable resistor 938 adjustably setting the low time constant of the function generator 886a, the variable resistor 922 providing a bias adjustment.

As shown in FIG. 18, there are two bleed paths around the capacitor 934: one bleed path going through the bias adjustment 922, the variable resistor 928, the resistor 926 and the diode 924; and the other bleed path going directly from the capacitor 934 across the variable resistor 938 and the resistor 936. Thus, in a forward biased position of the diode 926, the diode 926 is conducting and the function generator 886a has one bleed rate having a predetermined slope, and when the diode 924 is non-conducting, the bleed rate or, in other words, the slope of the discharge curve of the capacitor 934 is controllingly altered by changing the rate at which the capacitor 934 is being discharged.

In general, the function generator 886a is constructed to change the exponentially shaped discharge curve of the capacitor 934 to match a reciprocal curve, the reciprocal discharge curve being essentially a hyperbolically shaped curve. The exponentially shaped and the hyperbolically shaped curve are approximately the same during the initial discharging of the capacitor 934 and, therefore, the function generator 886a is, more particularly, constructed to initiate the shaping of the exponentially shaped discharge curve at some point after the capacitor 934 initially begins discharging, thereby essentially bending the exponentially shaped discharge curve of the capacitor 934 below this "so-called break point" to shape the discharge curve of the capacitor 934 to form an essentially hyperbolically shaped discharge curve therefor, for reasons to be made more apparent below.

The capacitor 934 is charged via the switching transistor 880 which was triggered "on" by the monostable multi-vibrator 876, in a manner described before. The capacitor 934 is subsequently discharged for the period of time between positive going zero crossings of the filter output and the monostable multi-vibrator 876 is in the deactivated status until triggered by a subsequent zero crossing detector output signal 679.

Thus, the zero crossing detector 362 provides an output trigger signal 679 to the input of the monostable multi-vibrator 876 thereby activating the monostable multi-vibrator 876 and biasing the switching transistor 880 in the "on" position to charge the capacitor 934 of the function generator 886. Since the capacitor 934 is charged in response to the zero crossing detector output signal 679 and allowed to discharge until the next zero crossing detector output signal 679, the voltage level of the charge remaining on the capacitor 934 will be proportional to the time between the zero crossings of the filter output signal or, in other words, a voltage proportional to the time between the zero crossings and of the sensed potential. The beginning of each monostable multi-vibrator timing period turns off the switching transistor 888 causing the voltage on the discharging capacitor 934 in the function generator 886a to be transferred to the memory capacitor 906, as will be described in greater detail below. The capacitor 874 cooperates with the resistors 870 and 872 producing a delay in turning on the switching transistor 880 after the beginning of the monostable multi-vibrator timing period. The capacitor 934 is charged for a period of time approximately equal to the monostable multi-vibrator timing period, a period of time sufficient to fully charge the capacitor 934. At the end of the monostable multi-vibrator timing period, the capacitor 934 is discharged through the resistive network of the function generator 886a, in a manner as described before. The resistive network of the function generator 886a alters or shapes the exponentially shaped discharge curve of the capacitor 934 to provide a reciprocal thereof or, in other words, to provide a discharge curve or voltage linearly proportional to the frequency of the incoming, sensed potential from the subject.

The output of the function generator 886 is thus going to be a control voltage linearly proportional to the frequency of the sensed, detected potential from the subject, and that control signal is connected to the collector of the switching transistor 887 having its emitter tied in common with the switching transistor 900, the switching transistors 887 and 900 operating in the nature of a switch in the tachometer network 370 during the operation of the bio-feedback apparatus 10b. The triggering of the switching transistor 888 to the "off" position or the "non-conducting" position provides a signal to the transformer 894, thereby biasing the switch formed by the switching transistors 887 and 900 to the "on" position, transferring the charge on the capacitor 934 to the memory capacitor 906 of the tachometer network 370. The capacitor 906, shown in FIG. 17, of the tachometer network 370 thus essentially operates in the nature of a memory capacitor 906, the switch formed by the transistors 887 and 900 providing a high impedance input to prevent the prematurely bleeding-off of the charge on the memory capacitor 906 during the operation of the bio-feedback apparatus 10b.

The transferred charge on the memory capacitor 906 of the tachometer network 370 is thus a voltage proportional to the frequency of the sensed, detected potential from the subject. The triggering of the switching transistor 888 or, in other words, the biasing of the switching transistor 888 to the non-conducting state is controlled via the output of the monostable multi-vibrator 876, since the base of the switching transistor 888 is tied to the output pin connection 834 of the multi-vibrator 876.

As mentioned before, the output of the multivibrator 876 at the pin connection 834 is connected to the pin connection 716 of the amplitude discriminator 364, shown in FIG. 16, for controlling the transferring of the charge on the capacitor 722 to the memory capacitor 736 of the amplitude discriminator 364. Therefore, the voltage proportional to the amplitude of the sensed, detected potential from the subject is transferred to the memory capacitor 736 at substantially the same time as the voltage proportional to the frequency of the sensed detected potential from the subject is transferred to the memory capacitor 906 of the tachometer network 370. The discharging of the memory capacitor 906 opens the FET switch 904 and connects the memory capacitor 906 in parallel with the output load resistor 910 to provide the tachometer network output signal 918 at the pin connection 916, the tachometer network output signal 918 being a d-c voltage linearly proportional to the frequency of the sensed, detected potential from the subject.

Shown in FIG. 19 is another embodiment of a function generator 886b connected in the tachometer network 370, shown in FIG. 17, in lieu of the function generator 886a, shown in FIG. 18. The function generator 886b, shown in FIG. 19, is more particularly, constructed to operate in the frequency range of 0.5 Hz. to 4.0 Hz.; however, the function generator 886b operates in the tachometer network 370 in a manner substantially the same as the function of the function generator 886a; that is, to provide an output signal linearly proportional to the frequency of the sensed potential from the subject for driving the switch formed by the switching transistors 887 and 900 to the "conducting" or "on" position and transferring the charge from a capacitor 940 of the function generator 886b to the memory capacitor 906 of the tachometer network 370. The function generator 886b includes a pin connection 942 which is connected to the collector of the switching transistor 880 and 887, in a manner similar to that described before with respect to the input pin connection 920 of the function generator 886a.

The input pin connection 942 of the function generator 886b is connected to a variable resistor 944 via a diode 946, a resistor 948 and a variable resistor 950. The variable resistor 944 is connected to the ground via a resistor 952, and to a negative power supply (not shown) at a pin connection 954 via a resistor 956.

A variable resistor 958 is connected to ground via a resistor 960, and the variable resistor 958 is connected to the negative power supply (not shown) at the pin connection 954 via a resistor 962. The variable resistor 958 is thus connected in series with the resistors 960 and 962 and this resistive network is connected in parallel with the resistive network formed by the variable resistor 944 and the resistors 952 and 956 (shown in FIG. 19). The variable resistor 958 is connected to the capacitor 940 via a variable resistor 964, a resistor 966 and a diode 968, the diode 968 being connected to the capacitor 940 generally between the input pin connection 942 and the diode 946.

A variable resistor 970 is connected to ground via a resistor 972, and is connected to the negative power supply (not shown) at the pin connection 954 via a resistor 974. The variable resistor 970 is connected to the capacitor 940, generally at a common connection between the capacitor 940 and the diode 968, and a variable resistor 976 connected in series to a resistor 978 is interposed between the variable resistor 970 and the connection between the variable resistor 970 and the common connection between the variable resistor 970, the capacitor 940 and the diode 968, as shown in FIG. 19.

The function generator 886b, shown in FIG. 19, is constructed to operate in a manner similar to that described before with respect to the function generator 886b, shown in FIG. 18, the salient difference being that the function generator 886b includes an intermediate control for shaping the exponentially shaped discharge curve of the capacitor 940 to a hyperbolically shaped curve linearly proportional to the frequency of the sensed potential from the subject. The variable resistor 964 controls the high limit of the time constant of the function generator 886b, the variable resistor 976 controls the low limit of the time constant of the function generator 886b, and the intermediate control (generally between the high and the low limit time constant settings) is provided via the variable resistor 950. Thus, the variable resistor 976 controls one bleed rate of the capacitor 940, the variable resistor 964 controls one other bleed rate of the capacitor 940 and the variable resistor controls yet another bleed rate of the capacitor 940.

When the monostable multi-vibrator 876 is activated via a trigger input at the pin connection 836 from the zero crossing detector 362, the switching transistor 880 is biased in the "on" position, thereby charging the capacitor 940 of the function generator 886b to a value equal to the negative power supply, the capacitor 940 then discharging to a voltage proportional to the period of time between the zero crossings of the sensed potential from the subject. The capacitor 940 is subsequently discharged, and initially both diodes 946 and 968 are conducting as the capacitor 940 discharges. The capacitor 940 will continue to discharge and, at some first break point preset by the variable resistor 964, the diode 968 will cut-off or stops conducting and, in this position, the capacitor 940 is discharging through the diode 946 and through the variable resistor 976 simultaneously, the low variable resistor 976 and the intermediate variable resistor 950 controlling the slope or rate at which the capacitor 940 is discharging. Subsequently, the capacitor 940 will discharge to a second break point where the diode 946 cuts off or stops conducting and, in this position, the capacitor 940 is discharging only through the low variable resistor 976, the low variable resistor 976 controlling the slope or the rate at which the capacitor 940 is discharging thereby shaping the discharge curve of the capacitor 940 to provide an output d-c voltage linearly proportional to the frequency of the sensed potential from the subject. Thus, the function generator 886b provides two distinct break points, the slope or rate of discharge of the capacitor 940 being changed at each break point. The two break points are utilized in the function generator 886b because of the substantially large range of signal frequencies received by the function generator 886b; that is, signal frequencies from approximately 0.5 Hz. to approximately 4.0 Hz. (a frequency range of approximately eight to one).

The function generator 886b operates in the tachometer network 370 (shown in FIG. 17) in a manner similar to that described before with respect to the function generator 886a, shown in FIG. 18, to transfer the charge on the capacitor 940 to the memory capacitor 906 of the tachometer network 370, the transferred charge on the memory capacitor 906 cooperating to provide the tachometer output signal 918, a d-c voltage linearly proportional to the frequency of the sensed potential from the subject. In one form (shown in FIG. 11), the output signal 388 of the tachometer network 370 is connected to the permanent recorder indicator 330, thereby providing a permanent chart-type feedback indication indicative of the frequency of the sensed potential from the subject, this particular feedback being provided for only one of the controlling channels 324 or 326, in one other form.

VOLTAGE CONTROLLED OSCILLATOR

The output signal 918 of each tachometer network 370 is connected to one of the voltage controlled oscillators 374 via pin connections 980 (FIG. 20) and 916 (FIG. 17), a preferred embodiment of a typical voltage controlled oscillator 374 being shown in FIG. 20. The voltage controlled oscillator 374 includes a non-inverting amplifier 982 having the positive input thereto connected to a variable resistor 984 and the negative input thereto connected to a resistor 986, the resistor 986 being connected to ground.

The negative input of the non-inverting amplifier 982 is connected to a variable resistor 988 via a resistor 990, the resistor 990 and the variable resistor 988, as shown in FIG. 20.

The variable resistor 988 is connected to a positive power supply (not shown) via a pin connection 992 and to a negative power supply (not shown) via a pin connection 984. The non-inverting amplifier 982 includes a feedback loop connected to an amplifier output signal 996 and to the negative input of the non-inverting amplifier 982, a feedback resistor 998 being interposed in the feedback loop.

The variable resistor 984 is connected to the non-inverting amplifier 982 such that a predetermined percentage of the incoming tachometer output signal 918 is connected to the positive input of the non-inverting amplifier 982. The variable resistor 988 provides a variable, controlled voltage to the negative input of the non-inverting amplifier 982 for providing the proper d-c offset therefor.

The non-inverting amplifier 982 thus provides a control voltage output signal 996 in response to the received tachometer output signal 918. The control voltage output signal 996 is connected to the negative input of a unity-gain type of inverting amplifier 1000 via a resistor 1002, the control voltage output signal 996 also being connected to one junction of a diode bridge network 1004 via a resistor 1006, as shown in FIG. 20.

The inverting amplifier 1000 provides an inverted output signal 1008 connected to one other junction of the diode bridge 1004 via a resistor 1010. The inverting amplifier 1000 includes a feedback loop between the output signal 1008 and the negative input thereto, a feedback resistor 1012 being interposed in the feedback loop.

The resistor 1002 and the feedback resistor 1012 are each sized to provide a precision gain control for the inverting amplifier 1000 such that the inverted output signal 1008 therefrom corresponds to the output signal 996 of the non-inverting amplifier 982; but, inverted with respect to polarity. The first diode bridge network 1004 is thus driven by the d-c control voltage output signal 918 from the tachometer network 370 by utilizing the unity-gain inverting amplifier 1000 to provide the opposite polarity signal.

The voltage controlled oscillator 374 also includes a second diode bridge 1014 having one junction connected to a positive power supply (not shown) via a pin connection 1016, a resistor 1018 being interposed between the second diode bridge 1014 and the pin connection 1016, and a negative power supply (not shown) connected to a pin connection 1020, a resistor 1022 being interposed between the second diode bridge 1014 and the pin connection 1020. One junction of the second diode bridge 1014 is connected to an output signal 1024 of an amplifier 1026, and one other junction is connected to the positive input of the amplifier 1026.

The amplifier 1026 includes a feedback loop between the output signal 1024 therefrom and the negative input thereto, a feedback resistor 1028 being interposed in the feedback loop. The negative input of the amplifier 1026 is connected to ground via a resistor 1030.

The output signal 1024 of the amplifier 1026 is connected to one junction of the first diode bridge 1004 and the opposite junction of the first diode bridge 1004 is connected to the negative input of an integrator amplifier 1032, the positive input to the integrator amplifier 1032 being connected to ground, as shown in FIG. 20. The integrator amplifier 1032 provides an output signal 1034 and a capacitor 1036 is connected between the output signal 1034 and the negative input of the amplifier 1032.

The integrator amplifier output signal 1034 is connected to the positive input of the amplifier 1026 via a variable resistor 1038, the positive input to the amplifier 1026 and the variable resistor 1038 each being connected to ground via a pair of diodes 1040 and 1042, the diodes 1040 and 1042 functioning to control the amplitude of the amplifier output signal 1024.

During the operation of the voltage controlled oscillator 374, the output signal 1024 of the amplifier 1026 alternates between a positive and a negative predetermined amplitude controlled by the two diodes 1040 and 1042 clamping the positive input of the amplifier 1026 to ground. When the amplifier output signal 1024 is positive, a positive input signal is applied to one junction of the diode bridges 1004 and 1014 simultaneously for positioning two of the diodes in each diode bridge 1004 and 1018 in the conducting state and the remaining two diodes being reversed biased, thereby connecting the positive control voltage output signal 996 to the integrator amplifier 1032 via the resistor 1006. In this position, the integrator amplifier output signal 1032 is driven at a linear slope in a negative going direction.

The integrator amplifier output signal 1034 will continue in a negative direction until the magnitude of the negative going integrator amplifier output signal 1034 is increased to a predetermined level to drive the positive input to the amplifier 1026 negative, thereby causing the amplifier output signal 1024 to switch from a positive to a negative signal. The variable resistor 1038 is interposed between the integrator amplifier 1032 and the amplifier 1026 to adjustably control the amplitude of the signal required to drive the amplifier 1026 in an opposite direction, thereby controlling the amplitude of the voltage controlled oscillator output signal 1034.

When the positive input of the amplifier 1026 is driven negative by the integrator amplifier output signal 1034, the amplifier output signal 1024 will go negative. In this position, the operation of the voltage controlled oscillator 374 is essentially reversed, since the first diode bridge 1004 will now be driven by a negative input voltage from the inverting amplifier 1000 connected thereto via the resistor 1010. When the first diode bridge 1004 is driven via the negative output signal 1008, a negative input signal is applied to the integrator amplifier 1032, thereby causing the voltage controlled oscillator output signal 1034 to be driven in the positive direction at a linear slope. The integrator amplifier output signal 1034 will continue going in a positive direction until the output signal 1034 reaches a predetermined, positive amplitude level causing the positive input to the amplifier 1026 to go positive, thereby switching the state of the amplifier output 1024 to the positive state, described before.

The two diode bridges 1004 and 1014, the amplifier 1026, the inverting amplifier 1000 and the integrating amplifier 1032 are each connected to provide an oscillating type of output signal 1034 which is triangularly shaped. The tachometer network output signal 918 thus controls the slope of the integrator amplifier output signal 1034 by applying different voltage inputs to the integrator amplifier 1032. Since the first diode bridge 1004 requires a positive supply voltage to one junction input and a negative supply voltage to the opposite junction input, the inverter amplifier 1000 is utilized to invert the control voltage signal 996 produced via the tachometer network output signal 916 in such a manner that the tachometer network output signal 918 controls the first diode bridge 1004 by supplying both the positive and the negative supply voltages thereto.

The voltage controlled oscillator 374 is further constructed to oscillate at a rate (the rate at which the integrator amplifier output signal 1034 changes slope) which is substantially equal to the frequency of the sensed potential from the subject multiplied by a predetermined factor, such as ten times the frequency of the sensed potential from the subject, for example.

In summary, the voltage controlled oscillator 374 converts the step type voltage of the tachometer network output signal 918 to a triangularly shaped voltage controlled oscillator output signal 1034 having a frequency equal to a predetermined multiple of the frequency of the incoming tachometer network output signal 918 and, since the tachometer network output signal 918 is linearly proportional to the frequency sensed potential from the subject, the voltage controlled oscillator output signal 1034 is proportional to the frequency of the sensed potential from the subject. The salient reason that the voltage controlled oscillator 374 is constructed to multiply the frequency of the tachometer network output signal 918 by a predetermined factor is to obtain a voltage controlled oscillator output signal 1034 oscillating at a frequency within the audible frequency spectrum.

The voltage controlled oscillator output signal 1034 is connected to the signal converter 376 which is constructed to receive the triangularly shaped wave form of the voltage controlled oscillator output signal 1034 and to convert that received signal shape to a substantially sine-wave shape of oscillating signal at the output pin connections therefrom 1046 and 1048. The output pin connection 1046 is connected to the automatic gain control 368 at the input pin connection 804 (shown in FIG. 16) via an a-c coupling voltage divider network comprising a capacitor 1050 connected in series with a resistor 1052 and a resistor 1054 connected between the resistor 1052 and the output pin connection 1046 and to ground.

The signal converter 376 is also connected to a positive power supply (not shown) at a pin connection 1056 via a resistor 1058 and a resistor 1060 is connected in parallel with the resistor 1058, the output pin connection 1048 being connected between the resistor 1050 and the signal converter 1076, as shown in FIG. 20. The signal converter output signal at the output pin connection 1048 is also substantially sine-wave shaped, and is 180 degrees out-of-phase with respect to the signal converter output signal at the pin connection 1046, the signal converter output signal 1048 being recorded or utilized for feedback, in some applications.

BANDPASS CONTROLLER

Each processing channel of the bio-feedback apparatus 10b includes a bandpass controller 372, a preferred embodiment of the bandpass controller 372 being shown in FIG. 21. The bandpass controller 372 receives one of the tachometer network output signals 918 via the input pin connection 1070. The tachometer network output signal 918 is connected to the base of a transistor amplifier 1072 via a resistor 1074, a resistor 1076 being connected to the base of the transistor amplifier 1072, generally between the resistor 1074 and the transistor amplifier 1072. The collector of the transistor amplifier 1072 is connected to a negative power supply (not shown) via a pin connection 1078, and the emitter of the transistor amplifier 1072 is connected to ground via a resistor 1080. The transistor amplifier 1072 is thus connected in the emitter-follower form to provide an impedance matching network 1082 for driving a low input impedance dual-comparator 1084, in a manner similar to that described before with respect to the comparator drive 560 and the dual-comparator 588, shown in FIG. 14.

The dual-comparator 1084 includes a first comparator amplifier 1086 and a second comparator amplifier 1088. The positive input of the first comparator amplifier 1086 is connected to the emitter of the transistor amplifier 1072, generally between the transistor amplifier 1072 and the resistor 1080 via a resistor 1090, the emitter of the transistor amplifier 1072 also being connected to the negative input of the second comparator 1088 via a resistor 1092. The negative input of the first comparator 1086 is connected to a variable resistor 1094, the variable resistor 1094 being connected to a negative power supply (not shown) via a pin connection 1096. The first comparator 1086 includes a feedback loop connected to the output signal thereof and to the positive input thereto and a feedback resistor 1098 is interposed in the feedback loop. The second comparator 1088 includes a feedback loop connected to the output signal therefrom and to the positive input thereto, a feedback resistor 1100 being interposed in the feedback loop around the second comparator 1088. The positive input to the second comparator 1088 is connected to a variable resistor 1102, the variable resistor 1102 being connected to a negative power supply (not shown) via a pin connection 1104.

The output signals of the first comparator 1086 and the second comparator 1088 are connected to provide a single, dual-comparator output signal 1106. The dual-comparator output signal 1106 is connected to one input of a first "NAND" gate 1108, the other input of the NAND gate 1108 being connected to a positive power supply (not shown) via a pin connection 1110.

The first NAND gate 1108 has an output signal 1112 which is connected to one input of a second NAND gate 1114, the other input of the second NAND gate 1114 being connected to an output signal 1116 from a third NAND gate 1118. One input of the third NAND gate 1118 is connected to the positive power supply (not shown) via the pin connection 1110, and the other input to the third NAND gate 1118 is connected to receive the first comparator output signal 756 from the comparator controller 366 (shown in FIG. 16). The second NAND gate 1114 provides the output signal 780 which is connected to the negative input of the second comparator 768 of the comparator controller 366, as described before with respect to FIG. 16. In one form, the output signal 1112 of the first NAND gate 1108 is connected to a portion of the audio output controller 354 via a pin connection 1120 for providing audio feedback in a manner to be made more apparent below.

During the operation of the bio-feedback apparatus 10b, the variable resistor 1094 adjustably sets an upper amplitude limit and the variable resistor 1102 adjustably sets a lower amplitude limit of the dual-comparator 1084. The dual-comparator 1084 constructed such that the dual-comparator output signal 1106 is in a "low" state when the tachometer network output signal 918 input thereto via the transistor amplifier 1072 is within the preset upper and lower amplitude limits of the dual-comparator 1084, and such that the dual-comparator output signal 1106 is in a "high" state when the tachometer network output signal 918 input thereto via the transistor amplifier 1072 exceeds or is outside the preset upper and lower amplitude limits of the dual-comparator 1084.

The bandpass controller 372 is thus controlled via a d-c voltage linearly proportional to the frequency of the sensed potential from the subject (the tachometer network output signal 918). The dual-comparator output signal 1106 is inverted via the first NAND gate 1108, and thus the output signal 1112 is "high" or one when the received tachometer network output signal 918 produces a dual-comparator output signal 1106 within the upper and the lower limits of the dual-comparator 1084, and the output signal 1112 is "low" when the received tachometer network output signal 918 produces a dual-comparator output signal 1106 outside the upper and the lower limits of the dual comparator 1084.

The third NAND gate 1118 receives the first comparator output signal 756 of the comparator controller 366 and, therefore, when the first comparator output signal 756 is positive or "high," the capacitor 784 starts charging through the resistor 782 (shown in FIG. 16). If both inputs to the second NAND gate 1114 are "high," the second NAND gate output signal 780 is "low." The NAND gate network comprising the first, the second and the third NAND gates 1108, 1114 and 1118 is thus essentially interposed between the first comparator 750 and the second comparator 768 of the comparator controller 366 and functions in the nature of a switch during the operation of the bio-feedback apparatus 10b.

Although the filter 360 of each processing channel provides a relatively selective frequency range for discriminating the signals to be processed in the separate processing channels of the bio-feedback apparatus 10b, the frequency proportional d-c control voltage provided via the tachometer output signal 918 if fed through the dual-comparator 1084, which provides a "high" dual-comparator output signal 1106 when the tachometer network output signal 918 exceeds the threshold level settings of the dual-comparator 1084, the dual-comparator 1084 functioning to further filter the varying potential input from the subject and having a substantially high rejection ratio (operating within a control frequency range at the upper and the lower limits of approximately one-fourth of a cycle, for example).

AUDIO FEEDBACK

A portion of the audio output controller 354 is schematically shown in FIG. 22, the audio output controller 354 having input pins 1124, 1126 and 1128. The input pin connection 1124 is connected to the pin connection 120 (FIG. 21) of the bandpass controller 372 (normally "high" and switched to "low" indicating signal presence); the input pin connection 1126 is connected to the comparator controller output signal 770 (normally "low" and switched to "high" indicating signal presence); and the input pin connection 1128 is connected to a positive power supply (not shown).

The input pin connection 1124 is connected to the base of a drive transistor 1132 via a diode 1134. The input pin connection 1126 is connected to the base of the drive transistor 1132 via a diode 1136, and a two position switch 1138 is interposed between the pin connection 1126 and the diode 1136. The input pin connection 1128 is connected to the base of the drive transistor 1132 via a diode 1140, and a two position switch 1142 is interposed between the diode 1140 and the pin connection 1128. The diodes 1134, 1136 and 1140 are, more particularly, connected in parallel to the base of the drive transistor 1132 and form a "diode-or" gate between the drive transistor 1132 and the incoming signals connected to the base thereof, wherein the drive transistor 1132 will be biased in the "off" position when any one of the diodes 1134, 1136 or 1140 is forward biased or conducting.

The emitter of the drive transistor 1132 is connectd to ground via a resistor 1144, and the collector of the drive transistor 1132 is connected to a positive power supply (not shown) via a pin connection 1146. A resistor 1148 is connected to the base of the drive transistor 1132 and to the positive power supply (not shown) via the pin connection 1146, and a resistor 1150 is connected to the base of the drive transistor 1132 and to ground.

The drive transistor 1132 is connected to a relay operated switch 1152 having a switch arm 1154 and an operating coil 1156 for energizing the relay operated switch 1152 in the "on" position of the drive transistor 1132. The operating coil 1156 is interposed in the connection between the collector of the drive transistor 1132 and the positive power supply (not shown), and a diode 1158 is connected in parallel across the operating coil 1156.

The relay coil 1156 operates the relay operated switch 1152 to connect the oscillating output signal at the pin connection 800 of the automatic gain control 368 (FIG. 16) to the audio feedback of the bio-feedback apparatus 10b, the output signal of the automatic gain control 368 being the voltage controlled oscillator output signal 1034 or, more particularly, the signal converter output signal (FIG. 20) having an automatically adjusted signal gain via the automatic gain control 368. The oscillating output signal from the automatic gain control 368 is connected to a capacitor 1160, an input pin connection 1162, and to an energized switch position 1164 of the relay operated switch 1152, the switch arm 1154 contacting a de-energized switch position 1168 in a deenergized position of the relay operated switch 1152 (shown in FIG. 22).

It should be particularly noted that the controlling signals connected to input pin connections 1124, 1126 and 1128, the interconnecting diode-or gate network, the drive transistor 1132 network, the relay operated switch 1152, the pin connection 1162, the switch arm 1154 and the two cooperating switch positions 1164 and 1168 have been shown in FIG. 22 for only one of the processing channels of one of the controlling channels 324 and 326. In the bio-feedback apparatus 10b, the above-mentioned portion of the audio feedback controller 354 is duplicated to receive controlling signals from all four of the processing channels of one of the controlling channels 324 and 326, each portion being connected and operating in a manner similar to that described above and below with respect to the one processing channel. More particularly, there are four switches 1138, each switch connected to the diode 1136 and to one of the comparator controller output signals 770, and the switches are mechanically connected for simultaneous positioning and the relay operated switch 1152 includes four switch arms 1154, each switch arm 1154 being operated via the relay coil 1152 simultaneously with the switch arm 1154 (shown in FIG. 22) to connect the oscillating output signal from one of the automatic gain controls 368 to the audio output controller 354 in an energized position of the relay operated switch 1152. It should be further noted that the portion of the audio controller 354, described above, is duplicated in the bio-feedback apparatus 10b to receive the four processing channels of the other one of the controlling channels 324 and 326, the four processing channels of each controlling channel 324 and 326 operating to independently activate a subject-perceivable audio feedback during the operation of the bio-feedback apparatus 10b, for reasons and in a manner to be made more apparent below.

In the energized position of the relay operated switch 1152, the oscillating output signals formed by the voltage controlled oscillators 374 and the signal converters 376 are each connected to one of the inputs of a mixer amplifier 1170 via a resistor 1172 and a variable resistor 1174, as shown in FIG. 22, Thus, in the "on" position of the switch 1142 and in the position of the switches 1138 disconnecting the pin connections 1126 from the diodes 1136 (only one pin connection 1126), one diode 1136 and one switch 1138 being shown in FIG. 22), the drive transistor 1132 will be continuously biased "on" independent of a detected signal presence in any of the processing channels, thereby energizing the relay operated switch 1152. When the switches 1138 are moved to the switch position connecting the pin connections 1126 to the diodes 1136, the drive transistor 1132 will be biased "on" only in response to a detected signal presence in any one of the four processing channels via the signal input to the pin connection 1124. The switches 1138 thus have one switch position wherein a subject-perceivable audio feedback signal is generated via the bio-feedback apparatus 10b even when the signal presence criteria of amplitude and duration indicates a no-signal presence, which may be useful in some applications.

The input of the mixer amplifier 1170, opposite the input thereof receiving the oscillating signals indicative of a signal presence in a particular processing channel is connected to ground via a resistor 1176, a mixer amplifier output signal 1173 being connected to the pin connection 1175. A feedback loop is connected between the mixer amplifier output signal 1173 and the signal input thereto, and a feedback resistor 1178 is interposed in the feedback loop.

The mixer amplifier output signal 1173 and the frequency of each oscillating signal produced in each processing channel of the controlling channels are sized with respect to the frequency ranges produced thereby in a manner similar to that described before with respect to the mixer or summing amplifier 72 (shown in FIG. 6) of the bio-feedback apparatus 10a, such that each output tone is subject-perceivable, yet produced simultaneously on the mixer amplifier output signal 1173 at the output pin connetion 1175. The mixer amplifier 1170 and the four processing channel input signals thereto via the resistors 1172 and the variable resistors 1174 provide the mixer amplifier output signal 1173 for one of the controlling channels 324 and 326. The bio-feedback apparatus 10b also includes a second mixer amplifier and the components connecting the four processing channel input signals thereto to provide the mixer amplifier output signal therefrom for the one other of the controlling channels 324 and 326 (only one being shown in FIG. 22 for the purpose of clarity of description).

The mixer amplifier output signal of one of the controlling channels 324 and 326 is connected to a pin connection 1182 (shown in FIG. 23), and to a first audio amplifier 1184 via conductors or signal paths 1183 and 1185 through a relay operated switch 1186. The mixer amplifier output signal of the other one of the controlling channels 324 and 326 is connected to pin connection 1188 and to a second audio amplifier 1190 via conductors or signal paths 1189 and 1191 through the relay operated switch 1186, as shown in FIG. 23. A switch 1192 has a first switch position 1194 and a second switch position 1196, the first switch position 1194 being connected to the pin connection 1182 via a conductor 1195 and the second switch position 1196 being connected to the pin connection 1188 via a conductor 1197.

Shown in FIG. 23, the relay operated switch 1186 includes an operating coil 1198 operably connected to a plurality of switch arms, generally designated by the reference 1200. The switch arms 1200 are each mechanically connected, and the switch 1186 has a mono-switch position 1202 and a stereo-switch position 1204, each of the switch arms 1200 being simultaneously switched to the mono-switch position 1202 and the stereo-switch position 1204 via the relay coil 1198, of the relay operated switch 1186.

The relay coil 1198 is connected to one switch arm of a mechanically operated switch 1208 via a resistor 1210, the mechanically operated switch 1208 having a plurality of switch arms (three of the switch arms being shown in FIG. 23) and each switch arm being associated with a mono-switch position 1212 and a stereo-switch position 1214.

One of the stereo-switch positions 1214 of the switch 1208 is connected to a positive power supply (not shown) via a conductor 1216 at a pin connection 1218, the conductor 1216 being also connected to the stereo-switch position 1214 of one of the other switch arms of the switch 1208 which is connected to a lamp indicator 1220 via a conductor 1222, as shown in FIG. 23.

The first audio amplifier 1184 receives an incoming signal via the conductor 1185 and provides an amplifier output signal 1226 connected to a first speaker 1228. The second audio amplifier 1190 receives an incoming signal via the conductor 1191 and provides an amplified output signal 1230 connected to a second speaker 1232. It should be particularly noted that the audio amplifier output signals 1226 and 1230 are also, in a preferred form, connected in parallel to a first and second earphone of a headset (not shown) to provide a subject-perceivable audio feedback following the first and the second speakers 1228 and 1232.

During the operation of the bio-feedback apparatus 10b, when the switch 1208 is moved to position the switch arm thereof in the stereo-switch positions 1214, the positive power supply (not shown) connected to the pin connection 1218 is connected to the relay coil 1198 energizing the relay operated switch 1186 and moving the switch arms 1200 thereof to the stereo-switch positions 1204. The switch 1192 may be in either position 1194 or 1196, shown in FIG. 23, and one of the controlling channel mixer amplifier output signals is connected to the first audio amplifier 1184 via the conductors 1183 and 1185 and the other one of the controlling channel mixer amplifier output signals is connected to the second audio amplifier 1190 via the conductors 1189 and 1191. Thus, in the energized stereo-position of the relay operated switch 1186 and in either position of the switch 1192, the first speaker 1228 provides subject-perceivable audio feedback signals indicative of the presence of signals within predetermined frequency bands of the detected potential from the subject via one of the electrodes 314 and 318, and the second speaker 1232 provides subject-perceivable audio output indications indicative of the presence of signals within predetermined frequency bands in the detected potential from the subject via the other one of the electrodes 314 and 318. In this stereo-position of the mechanically operated switch 1208, the lamp indicator 1220 is also connected to the positive power supply via the conductors 1222 and 1216, thereby providing a visual output indication indicative that the biofeedback apparatus 10b is operating in the stereo-mode.

When the switch arms of the switch 1208 are each moved to the mono-switch positions 1212, the relay coil 1198 is de-energized thereby moving each of the switch arms 1200 to the mono-switch positions 1202. In the mono-switch position of the relay operated switch 1186, the controlling channel mixer amplifier output signals at the pin connection 1182 and 1188 are selectively switched to the audio amplifiers 1184 and 1190 by the switch 1192, switch 1192 being a section of the left-right select relay under control of the left-right select switch. In this position of the switch 1186, one of the controlling channel mixer amplifier output signals is connected to each of the audio amplifiers 1184 and 1190 by moving the switch 1192 to the switch position 1194 or 1196, the switch 1192 being utilized to select one of the controlling channels 324 and 326 to control the aduio feedback.

ANALOG SWITCH AND DELAY SIGNAL CONTROLLER

The output signal 770 of the comparator controller 366 in each processing channel of one of the controlling channels 324 and 326 is connected to the analog switch 420 of the data reduction controller 344 (FIGS. 10 and 12) and, more particularly, to one of the input pin connections 1240 thereof, as shown in FIG. 24. Each input pin connection 1240 is connected to one switching transistor 1242 via a resistor 1244, the emitter of each switching transistor being connected to ground and the collector of each switching transistor 1242 being connected to the gate of one of the FET switches 1246 via a resistor 1248. The gate of each FET switch 1246 is also connected to a positive power supply (not shown) at the pin connection 1250 via a resistor 1252, the output signal 438 from the delay oscillator 422 (shown in FIG. 12) being connected to the pin connection 1255 of the analog switch 420. As shown in FIG. 24, the source connection of each of the FET switches 1246 are connected in common and the drain connection of each of the FET switches 1246 is connected to one of the output pin connections 1254, each of the output pin connections 1254 of the analog switch 420 being connected to one recording channel of the delay signal controller 424.

Thus, each of the FET switches 1246 are biased in the "closed" position in a non-conducting or "off" position of the switching transistor 1242 connected thereto and are each biased in the "open" position in a conducting or "on" position of the switching transistor 1242 connected thereto. Each switching transistor 1242 receives the output signal 770 from one of the comparator controllers 366, the comparator controller output signals 786 biasing the switching transistor 1242 connected thereto into the "on" or conducting position and opening the FET switch 1246 connected thereto when a signal presence is detected in the processing channel having the predetermined signal amplitude and duration controlled by the feedback signal controller 334. In the "open" position of the FET switches 1246, the output signal 438 from the delay oscillator 422 is connected to one of the recording channels of the delay signal controller 424 via the output pin connections 1254, each switching transistor 1242 controlling the position of the FET switches 1254 connected thereto.

The delay signal controller 424 (FIG. 12) receives the output signals from the analog switch 420 at the pin connections 1254 (shown in FIG. 24), each recording channel of the delay signal controller 424 being connected to one of the pin connections 1254 to receive the delay oscillator output signal 438 indicating signal presence in one particular processing channel of one of the controlling channels 324 and 326. The delay oscillator output signal 438 is recorded for a predetermined period of time, referred to as an "epoch" interval of time. Thus, each recording channel of the delay signal controller 424 has recorded signal presence in the processing channels, the recorded signal presence being retained by the delay signal controller 424, and subsequently connectd to the overvoltage controller 426, during the operation of the bio-feedback apparatus 10b.

In one form, the delay signal controller 424 can be a tape recorder having four recording channels and four playback channels, a loop being made in the tape between the recording heads defining the epoch period of time. In one other form, digital shift registers can be utilized to develop the delay signal controller output signal 442, the digital shift registers being also connected to receive the clock pulse 446 for controlling the shifting position of each of the digital shift registers. In this latter form, the signal synchronization is enhanced since the delay oscillator 422 would no longer be required and the digital circuitry would all be controlled by the single clock pulse generator 430.

OVERVOLTAGE CONTROLLER

The overvoltage controller 426 receives the delayed signals 442 from the delay signal controller 424, recorded over the last predetermined epoch period of time, the delayed output signals 442 being, more particularly, connected to an overvoltage comparator 1260, shown in FIG. 25. The overvoltage comparator 1260 is constructed similar to the dual-comparator 1084 of the comparator controller 372 (shown in FIG. 21 and described before), the overvoltage comparator 1260 having an output signal 1262 which is normally "low" and which is switched to a "high" state when receiving an output signal 442 from the delay signal controller 424 within the upper and the lower amplitude limits set by the variable resistor adjustments of the dual-comparator of the overvoltage comparator 1260.

The output signal 1262 of the overvoltage comparator 1260 is connected to the base of a switching transistor 1264 by a resistor 1266, the emitter of the switching transistor 1264 being connected to ground and the collector of the switching transistor 1264 being connected to a positive power supply (not shown) via a pin connection 1268 and a resistor 1270. The collector of the switching transistor 1264 is connected to the base of a switching transistor 1272 via a resistor 1274, the emitter of the switching transistor 1272 being connected to ground and the collector of the switching transistor 1272 being connected to a positive power supply (not shown) via a pin connection 1267 and a resistor 1278.

The collector of the switching transistor 1272 is connected to the anode of a diode 1280, the cathode of the diode 1280 being connected to a transistor amplifier 1282 via a resistor 1284, and a variable resistor 1286 connected in parallel with a capacitor 1288 is connected in parallel with the resistor 1284 of the transistor amplifier 1282, as shown in FIG. 25.

The transistor amplifier 1282 is connected in the emitter-follower form, the collector of the transistor amplifier 1282 being connected to a positive power supply (not shown) via a pin connection 1290 and the emitter of the transistor amplifier 1282 being connected to an output pin connection 1292 having a resistor 1294 connected in parallel thereto to ground. It should be noted that the portion of the overvoltage controller 426 shown in FIG. 25 is constructed for only one of the processing channels of one of the controlling channels 324 and 326, and there is one such portion for receiving signals from each of the four processing channels of the controlling channels 324 and 326 in the bio-feedback apparatus 10b.

When the overvoltage comparator 1260 is receiving an output signal 442 from the delay signal controller 424, the overvoltage comparator output signal 1262 is in the "high" state biasing the transistor amplifiers 1264 and 1272 to the "on" or conducting position, the oscillator delay signal controller output signal 442 being utilized to generate a d-c output control voltage signal at the emitter of the transistor amplifier 1282 or, in other words, at the output pin connection 1292.

COUNTER CONTROLLER, COUNTERS AND DIGITAL/ANALOG CONVERTER

A preferred embodiment of one of the counter controllers 428 of the bio-feedback apparatus 10b is schematically shown in FIG. 26, the counter controller 428 having an input pin connection 1300 receiving the clock pulse 446 generated by the clock pulse generator 430 (shown in FIG. 12); an input pin connection 1302 receiving a signal 1304 controlled by the comparator controlling output signal 770 connected at pin 1418 (shown in FIG. 28), the signal 1304 at the input pin connection 1302 being in the "high" state when signal presence is detected in the processing channel connected thereto; and an input pin connection 1306 connected to and receiving the control voltage output signal 444 of the overvoltage controller provided at the pin connection 1292 (shown in FIG. 25).

The clock pulse 446 is connected to a plurality of series-connected inverting gates 1308, the output signal of the last of the series-connected inverting gates 1308 being connected to one input of a four-input first NAND gate 1310. The plurality of inverting gates 1308 are interposed in the clock pulse 446 input line to the first NAND gate 1310 to delay the clock pulse for a predetermined interval of time for aligning the clock pulse 446 with the other control signals in the logic circuitry of the counter controller 428. The control signal 1304 connected to the input pin connection 1302 is connected to one other input of the four-input first NAND gate 1310 via a conductor 1312, the conductor 1312 also being connected to an output pin connection 1314 for controlling the "up" count position of the counters 432, as will be made more apparent below.

The overvoltage controller output signal connected to the pin connection 1306 is connected to one input of a second four-input NAND gate 1320, and the clock pulse 446 from the last series-connected inverting gate 1308 is connected to one of the inputs of the second four-input NAND gate 1320. The control signal on the conductor 1312 is connected to an inverter 1322, the output of the inverter 1322 being connected to one of the inputs of the NAND gate 1324, and one of the inputs of the second four-input NAND gate 1320. The control signal on the conductor 1318 is connected to an inverter 1326, the ouput of the inverter 1326 being connected to the other input of the NAND gate 1324 and to one of the inputs of the four-input NAND gate 1310. The output of the NAND gate 1316 and the output of the NAND gate 1324 are each connected to one of the inputs of a NAND gate 1328, the output of the NAND gate 1328 being connected to a NAND gate 1330 and the other input of the NAND gate 1330 being the clock pulse received at the pin connection 1300 of the counter controller 428. The gates 1316, 1324 and 1328 are connected in an exclusive "OR" configuration. The gates 1322 and 1326 are used to produce the "NOT" functions as the signals connected to the pin connections 1302 and 1306, respectively.

The output of the NAND gate 1330 is connected to and received by a monostable multi-vibrator 1332, the output of the monostable multi-vibrator 1332 being connected to one of the inputs of the first and second four-input NAND gates 1310 and 1320. The monostable multi-vibrator 1332 is utilized to inhibit the clock pulse at the last gate of the delay line (comprising the gates 1308) from clocking the counter at the change over of count directions for the first clock pulse to substantially maintain the count correct. The output signals from the first and the second four-input NAND gates 1310 and 1320 are each connected to one input of a NAND gate 1334. The output signal of the NAND gate 1334 is connected to an output connection 1335, the output signal at the pin connection 1335 being the clock pulse 446, in one position. The inverted output signal 1304 from the inverter 1322 is connected to an output pin connection 1336 for controlling the "down" count of the counters 432.

As shown in FIG. 27, the counters 432 have input pin connections 1340, 1342, and 1344; the pin connection 1340 being connected to the pin connection 1335 (FIG. 26) and receiving the clock pulse 446; the pin connection 1342 connected to the pin connection 1314 (FIG. 26) and receiving the up-count signal from the counter controller 428; and the pin connection 1344 connected to the pin connection 1336 and receiving the down-count control signal from the counter controller 428. The counters 432, in a preferred form, are a commercially available up-down type of counter such as the binary up-down serial carrier counter available from such companies as Texas Instruments Company of Dallas, Texas.

The counters 432 have three modes of operation: count-up, count-down, and no-count, the operational modes of the counters 432 being controlled via the received signals at the input pin connection s 1340, 1342 and 1344 of the counters 432. The counters 342 are positioned in the count-up mode to count up to a predetermined number in response to a received clock pulse 446 at the pin connection 1340, a received count-up signal at the pin connection 1342 indicating a sensed signal presence of a predetermined minimum amplitude and duration producing a comparator controller output signal 770 and no delayed signal presence producing a delay signal controller output signal 442. The counters 432 are positioned in the count-down mode in response to a received clock pulse 446 at the pin connection 1340, and a received count-down signal at the pin connection 1344 indicating a delay signal presence of a predetermined minimum amplitude and duration producing a delay signal controller output signal 442 and no signal presence for producing a comparator controller output signal 770. The counters 432 are positioned in the no-count mode when the comparator controller 366 is producing an output signal 770 indicating signal presence of a predetermined minimum amplitude and duration and the delay signal controller 424 is producing an output signal 442 indicating a delayed signal presence of a predetermined minimum amplitude and duration; the counters 432 being also positioned in the no-count mode when there is no signal presence for producing the comparator controller output signal 770 and no delayed signal presence for producing the delay signal controller output signal 442.

The counters 432 are, in one form, connected to provide an eight-bit output signal each bit being connected to one of the counter output pin connections, generally designated by the reference 1346 in FIGS. 27 and 28. The output bit signals 1346 are, in a preferred form, NOT signals or, in other words, each output bit signal is "low" indicating a counted bit and "high" indicating a zero.

The counter output bit signals at the pin connections 1346 are each connected to the digital/analog converter 434 and, more particularly, each output bit from the counter 432 is connected to the base of one of the switching transistors 1348 via a resistor 1350, as shown in FIG. 27. The emitter of each of the switching transistors 1348 is connected to ground and the collector of each of the switching transistors 1348 is connected to a positive power supply (not shown) at a pin connection 1352 via a resistor 1354. The collectors of the switching transistors 1348 are connected in parallel to an operational amplifier 1356 via a voltage dropping resistor 1358, 1360, 1362, 1364, 1366, 1368, 1370 and 1372, respectively. The voltage dropping resistors 1358 through 1372 provide a controlled current to the current node of the operational amplifier 1356, and are sized to provide a predetermined, controlled voltage drop there-across such that the total input signal to the operational amplifier 1356 provides an operational amplifier output signal 1374 indicative of the total count from the counters 432.

The output signal 1374 from the operational amplifier 1356 is connected to the base of a transistor amplifier 1380 via a resistor 1382, the operational amplifier 1356 thus providing the base biasing for the transistor amplifier 1380. The transistor amplifier 1380 is connected in the emitter-follower form such that a current flows across a resistor 1384 connected to the emitter thereof, the resistor 1384 being connected to a negative power supply (not shown) via a pin connection 1386. The collector of the transistor amplifier 1380 is connected to a positive power supply (not shown) at a pin connection 1388 via a resistor 1390.

The output signal of the digital/analog converter 434 is taken at the pin connection 1392 which is connected to the emitter of the transistor amplifier 1380. A feedback loop is connected about the digital/analog output signal at the pin connection 1392 and to the input signal to the operational amplifier 1356, a feedback resistor 1394 being interposed in the feedback loop.

The other input of the operational amplifier 1356 is connected to ground via a resistor 1396, and a diode 1398 to the operational amplifier 1356 input signal and to ground in parallel with the resistor 1396. The resistors 1358-1372 are also connected in parallel to a variable resistor 1400 via current limiting resistor 1401, the variable resistor 1400 being connected to a positive power supply (not shown) via a pin connection 1402 and to a negative power supply (not shown) via a pin connection 1404.

The digital/analog converter 434, shown in FIG. 27, receives the counter output signal 450 (each counter output bit being "high" when the counter connected thereto has a zero count thereon) via the pin connections 1346, and each "high" counter output signal at the pin connection 1346 connected thereto biases the switching transistor 1348 connected thereto "on." In the "off" or "non-conducting" position of any of the switching transistors 1348, the voltage drop across the resistor 1358-1372 connected to the "non-conducting" switching transistor is controlled by the reference voltage supplied via the pin connection 1352, thereby controlling the input signal to the operational amplifier 1356, as will be made more apparent below.

The voltage dropping resistors 1358-1372 are sized such that, when each of the switching transistors 1348 is biased "on," indicating all of the counters have been reset to zero, the output signal at the pin connection 1392 indicates a "zero" count, the variable resistor 1400 being initially adjusted to set the output signal 1374 of the operational amplifier 1356 to provide zero count indication at the pin connection 1392.

During the operation of the bio-feedback apparatus 10b, when one of the output pin connections 1346 is "low" indicating a count on the counter connected thereto, the switching transistor 1348 connected to that counter output pin connection 1346 is biased "off." In the "non-conducting" or "off" position of any one of the switching transistors 1348, the resistor 1358-1372 connected to the conducting switching transistor 1348 is then connected in series with the resistor 1354 connected thereto causing a voltage drop thereacross connecting a positive signal to the current node of the operational amplifier 1356. When the operational amplifier 1356 receives a positive signal at the current node thereof, the diode 1398 will be forward biased and conducting, and the voltage drop thereacross is applied to the positive input of the operational amplifier 1356. The operational amplifier output signal 1374 is proportional to the current being supplied to the current node thereof which is controlled by the resistive values of the resistors 1358-1372 connected to the switching transistors 1348 in the non-conducting or "off" position.

The operational amplifier 1356 provides the base biasing for the transistor amplifier 1380 which is connected in the emitter-follower form providing an output current across the resistor 1384 for controlling the digital/analog converter output signal 452 at the pin connection 1392. The digital/analog converter output signal 452 is thus an analog d-c voltage indicative of the count from the counters 432, thereby being indicative of a detected signal presence or, more particularly, an average percentage of signal presence detected in one of the preceding epochs of time compared with the signal presence being then detected in that particular processing channel.

In the operation of the bio-feedback apparatus 10b, there is one digital/analog converter 434 connected in each processing channel, in one form. In one preferred form, each digital/analog converter output signal 452 is connected to a meter light projection device for providing a visual feedback, each of the light projection devices having a meter movement consisting of a light projected on a screen via a translucent, colored bar wherein the screen is preferably colored green and the translucent bar is preferably colored red so that a black bar is projected on the screen, the movement of the black bar providing a visual feedback indicative of the percentage of signal presence produced by the subject for the preceding epoch of time in the processing channel connected thereto.

One other portion of the counter controller 428 is shown schematically in FIG. 28, this logic gating portion of the counter controller 428 being referred to before with respect to FIG. 26 and the comparator controller controlled signal 1304. More particularly, the output bit signals from the counters 432 at the pin connections 1346 (shown in FIGS. 27 and 28) are each connected to a multiple-input NAND gate 1410.

The multiple input NAND gate 1410 provides an output signal in a "high" state if any one of the input signals thereto from the counters 432 is in a "low" state or a digital zero. The output signal from the multiple-input NAND gate 1410 is connected to one of the inputs of a NAND gate 1412, the other input to the NAND gate 1412 being provided via the output signal of a NAND gate 1414. One of the inputs of the NAND gate 1414 is connected to a positive power supply (not shown) via a pin connection 1416 and the other input to the NAND gate 1414 is connected to the comparator controller output signal 770 via the pin connection 1418. The output signal 1304 from the NAND gate 1412 is provided at an output pin connection 1420.

Thus, when the comparator controller output signal 770 at the pin connection 1418 is "high," the output signal from the gate 1414 is "low." In this position, when all of the counter output pin connection 1346 is "high" indicating a zero count on the counters 432, the output of the multiple-input NAND gate 1410 is "low," thereby providing an output signal 1304 in the "high" state at pin connections 1420 (FIG. 28) and 1312 (FIG. 26) and at the pin connection 1314 providing a "high" count-up signal to the counters 432. In this same position of the counter output signals, when the comparator output signal 770 is "low," the output signal 1304 of the NAND gate 1412 is "high," thereby providing an output signal at the "high" count-up signal at the pin connection 1314 to the counters 432. Thus, if the counter has a zero count, the counter is prevented from counting down under any given control signal and, therefore the counter cannot count from zero to a maximum in one step. The count-up from zero count control assures that noise will not produce an erroneous output signal or percentage.

The operation of the portions of the counter controller 428 shown in FIGS. 26 and 28 is illustrated in TABLE I, below, wherein:

A "low" state is represented by a digital 0;

A "high" state is represented by a digital 1;

The clock pulse is represented by the combination 10; and

The inverted clock pulse is represented by the combination 01. ##SPC1##

The counters 432 will count-up when signal presence is indicated by a comparator controller output signal 770 and delay signal controller 424 is not producing an output signal 442. If the signal presence indicated by the comparator controller output signal 770 continues to exist for the epoch of time, the counters 432 will count-up to the full preset count; and, if the signal presence indicated by the comparator controller output signal 770 continues, the counter controller 428 will be receiving the signal presence indicated by the comparator controller output signal 770 and the delay signal presence via the delay signal controller output signal 442, thereby activating the counter controller 428 to position the counter 432 in a no-count position holding the full count thereon indicating the subject is producing one predetermined signal component 100 per cent. In this position, the comparator controller output signal 770 must return to a "low" state before the delay signal controller output signal 442 will then start the counters 432 counting down. If the comparator controller output signal 770 remains in the low state for the epoch of time, the delay signal controller output signal 442 will cause the counters 432 to count down to a zero count. At that point, the counters 432 will be forced to an up count state by the action of the count control circuitry of FIG. 28. By the same token, if the signal presence indicated by the comparator controller output signal 770 is again returned to the "high" state and if a delayed signal presence is still being produced via the delay signal controller output signal 442, the counters 432 will be positioned in a no-count position and the percentage indicated will be held thereon. Thus, the data reduction controller 344 of the bio-feedback apparatus 10b is constructed such that the delayed signal presence indicated by the delay signal controller output signal 442 is essentially compared with the signal presence indicated by the comparator controller output signal 770 to produce a sliding epoch, the count on the counters 432 produced via the presence signal being indicative of the average percentage of signal presence produced by the subject during the preceding epoch of time.

In the "zero" position of each of the counters 432, the multiple-input NAND gate 1410 and the gates 1414 and 1412 cooperate such that the clock pulse is connected to the counters 432 in only one position; that is, when a signal presence exists via the comparator controller output signal 770 and the delay signal controller 424 is not producing an output signal 442. In this position, the counter controller 428 connects the clock pulse 446 and the count-up signal via the pin connection 1314 to the counters 432, as indicated in TABLE I above. The multiple-input NAND gate 1410 and the gates 1414 and 1412 prevent the counters 432 from counting down through zero and indicating a false reading full count.

The NOT outputs at the pin connections 1346 are connected to the digital/analog converter 434 and, thus, the pin connections 1346 are in the "high" state when the counter of the counters 432 connected thereto has a zero count thereon. In the "low" state of any of the counter pin connections 1346, the switching transistor 1348 is biased in a "non-conducting" position, thereby supplying current to the current node of the operational amplifier 1356 via one of the voltage dropping resistors 1358 through 1372 connected to the non-conducting switching transistor 1348. The resistance value of voltage dropping resistor determines the current supplied to the operational amylifier 1356 and the operational amplifier 1356 converts the received current to an analog voltage at the output signal 1374 therefrom for driving the transistor amplifier 1380, thereby providing a negative analog voltage at the output pin connection 1392.

The foregoing description of the counter controller 428, the counters 432 and the digital/analog converter 434 has been directed to one processing channel of one of the controlling channels 324 and 326, for the purpose of clarity of description. In the bio-feedback apparatus 10b there are counter controllers, counters, and digital/analog converters for controlling feedback in each of the four processing channels of each of the controlling channels 324 and 326 or, in one form, for controlling the feedback in each of the four processing channels of one preselected controlling channel 324 or 326.

VISUAL FEEDBACK

A portion of the visual output controller 348 is shown in FIG. 29 and basically comprises: a meter drive network 1426 including an operational amplifier 1428 having the positive input connected to a variable resistor 1430 and the negative input connected to a variable resistor 1432 via a resistor 1434, the connection between the negative input of the operational amplifier 1428 and the variable resistor 1432 being connected to ground via a resistor 1436.

The variable resistor 1430 is connected to ground on one side thereof and the opposite side is connected to a pin connection 1438 to provide the input signal to the operational amplifier 1428, the input signal being provided via the digital/analog converter output signal 452 (FIG. 12). A feedback resistor 1440 is connected to the output signal 1442 and to the negative input of the operational amplifier 1428, thereby providing a feedback loop about the operational amplifier 1428. A diode 1444 is connected in parallel with the feedback resistor 1440 and a diode 1446 is connected to the negative input of the operational amplifier 1428, the cathode of the diode 1446 being connected to a variable resistor 1448. The variable resistor 1448 is connected to a negative power supply (not shown) at a pin connection 1450 via a resistor 1452. The variable resistor 1432 is connected to a negative power supply (not shown) at a pin connection 1454 via a resistor 1456. The output signal 1442 of the operational amplifier 1428 is connected to a meter 1458 and to an output pin connection 1460, which in a preferred form is connected to the permanent recorder indicator 330 (shown in FIG. 11).

The digital/analog converter output signal 452 drives the operational amplifier 1428, the operational amplifier output signal 1442 being connected to the meter 1458 such that the meter needle deflection provides a visual feedback indicative of the average percentage of time during the epoch when a signal presence was being produced in the processing channel connected thereto. The variable resistor 1430 controls the total deflection of the meter 1458 by controlling the input signal to the operational amplifier 1428, the diodes 1444 and 1446 control the limits of the output signal 1442, thereby providing a meter deflection protection to preventing overdriving the meter 1458. The portion of the visual feedback controller 348 is shown in FIG. 29 for controlling one of the processing channels, the biofeedback apparatus 10b, in one form, including duplicate portions for controlling visual feedback in each of the processing channels.

Another portion of the visual output controller 348 is shown in FIG. 30, and includes a frequency meter drive network 1461 having a pin connection 1462 connected to a negative power supply (not shown), the pin connection 1462 being connected to a resistor 1464 in series, with a voltage divider network 1466. The voltage divider network 1466 is connected to a mechanically operated switch having a switch arm 1468 via three switch positions 1470, 1472 and 1474, each switch position connecting a different, predetermined negative bias through the switch arm 1468 when the switch arm 1468 is selectively switched into contact therewith.

The switch arm 1468 is connected to one contact of a relay 1476 having a relay arm 1478, the other relay contact being connected to receive the tachometer network output signal 378 via a pin connection 1480. The relay 1476 has an operating coil 1482 connected to a positive power supply (not shown) at a pin connection 1484 via a resistor 1486, the operating coil 1482 being also connected to the collector of a switching transistor 1488. The emitter of the switching transistor 1488 is connected to ground, and the base is connected to receive the comparator controller output signal 770 at the pin connection 1490 via a resistor 1488.

The relay arm 1478 is connected to a meter drive 1494 driving a meter 1496 connected thereto. The meter drive 1494 and the meter 1496 are constructed and operate similar to the meter drive 1426 and the meter 1458, shown in FIG. 29 and described before.

The tachometer output signal 378 is connected to the normally open contact of the relay 1476 and, when a "high" comparator controller output signal 770 is connected to the switching transistor 1488, the switching transistor 1488 is biased "on" energizing the relay coil 1482 and connecting the tachometer output signal 378 to the meter drive 1494 via the relay arm 1478. In this position, the meter 1496 provides a visual feedback indicative of the frequency of the signal component in the processing channel connected thereto when the comparator controller output signal 770 is "high" indicating signal presence in the processing channel.

In the de-energized position of the relay coil 1482, the relay arm 1478 engages the relay contact connecting the voltage divider network 1466 to the meter drive 1494. The switch positions 1470, 1472 and 1474 of the voltage divider network 1466 provide a centering bias to the meter drive 1494, in the de-energized position of the relay 1476 to prevent meter-needle movement or, in other words, to drop the meter needle back to a preset centered position. The portion of the visual output controller 348 is shown in FIG. 30 for controlling visual feedback in one of the processing channels, the bio-feedback apparatus 10b, in one form, including duplicate portions for controlling visual feedback in each of the processing channels.

One other portion of the visual output controller 348 is schematically shown in FIG. 31, having input pin connections 1500, 1502, 1504, and 1506 each connected to one of the comparator controller output signals 770 of each processing channel, each input pin connection being connected to one of the switching transistors 1508 via a resistor 1510. The collector of each switching transistor 1508 is connected to one of the relay coils 1512 of a relay 1514 via a resistor 1516, and a diode 1518 is connected in parallel with each relay coil 1512. The energized contact position of each relay 1514 is connected to a lamp indicator (not shown) at one of the output pin connections 1520, 1522, 1524 and 1526, and each relay contact arm is connected to a power supply (not shown) via a pin connection 1528.

Thus, when signal presence is indicated in any one of the processing channels the comparator controller output signal 770 of that processing channel biases one of the switching transistors 1508 "on" energizing the relay coil 1512 connected thereto and moving the relay 1514 to the energized position. In the energized position, the lamp indicator (not shown) is connected to the power supply (not shown) via the pin connection 1528 and the pin connection 1520, 1522, 1524 or 1526 connected to the energized relay 1514, thereby providing a visual output indication indicative of signal presence of a predetermined minimum amplitude and duration in one of the processing channels. The portion of the visual output controller 348 shown in FIG. 31 controls the visual feedback for four of the processing channels of one of the controlling channels 324 and 326, the bio-feedback apparatus 10b, in one form, including a duplicate portion for controlling visual feedback for the one other of the controlling channels 324 and 326.

Changes may be made in the construction and the arrangement of the various parts or the elements of the embodiments as disclosed herein without departing from the spirit and scope of the invention as defined in the following claims.

Claims

What is claimed is:

1. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing feedback signals in response thereto, the apparatus comprising:

a brain-wave indicator detecting and sensing brain-wave potentials, and providing an output signal responsive thereto;

a preamplifier receiving the brain-wave indicator output signal and providing an amplified output signal responsive thereto;

a plurality of processing channels, each processing channel receiving the preamplifier output signal and providing a feedback signal responsive thereto, each processing channel comprising:

a passband filter, having a predetermined passband, receiving the preamplifier output signal and providing an output signal responsive to a frequency component of the received signal within the passband; and

means receiving the passband filter output signal and providing an output signal indicative of signal presence in the processing channel, including:

an oscillator, interposed in each processing channel, each oscillator in each processing channel receiving the passband filter output signal and generating an output signal having a distinct, separately identifiable frequency in response thereto, the oscillator output signals indicating signal presence in the processing channels;

a feedback indicator receiving the output signals indicative of the signal presence from each of the processing channels and providing subject-perceivable feedback signals responsive thereto, the feedback indicator including:

a summing amplifier receiving the oscillator output signal from each of the oscillators in each processing channel and providing a single output signal in response to the received oscillator output signals; and

an output indicator receiving the summing amplifier output signal and providing a subject-perceivable output indication responsive thereto.

2. The bio-feedback apparatus of claim 1 wherein the means receiving the passband filter means output signal is defined further to include:

a full-wave rectifier providing an output signal in response to a received input signal;

means connected to the full-wave rectifier receiving the passband filter output signal and providing an input signal to the full-wave rectifier;

a timing network receiving the full-wave rectifier output signal and providing a feedback control voltage in response to a received signal of a predetermined minimum duration thereby substantially eliminating feedback indications produced via relatively short duration sensed brainwave potentials; and

switch means having an "on" and an "off" condition connected to the timing network and the oscillator, the switch means receiving the feedback control voltage and being biased in the on condition in response thereto activating the oscillator in the "on" condition, the oscillator providing the output signal indicating signal presence in the processing channels.

3. The bio-feedback apparatus of claim 2 wherein each processing channel is defined further to include:

an amplifier receiving the preamplifier output signal and providing an amplified output signal in response thereto; and

sensitivity adjustment means connected to the amplifier controlling the threshold sensitivity setting of the amplifier connected thereto, the amplifier providing an amplifier output signal in response to a received preamplifier output signal having an amplitude exceeding the threshold setting of the sensitivity adjustment means connected thereto.

4. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing the feedback signals in response thereto, the apparatus comprising:

a brain-wave indicator sensing the brain-wave potentials, and providing an output signal responsive thereto;

a preamplifier receiving the brain-wave indicator output signal and providing an amplified output signal responsive thereto;

a plurality of processing channels, each processing channel receiving the preamplifier output signal and providing a feedback signal responsive thereto, each processing channel comprising:

a passband filter, having a predetermined passband, receiving the preamplifier output signals and providing an output signal responsive to a frequency component of the received signal within the filter passband;

means receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel, including:

comparator means, having an upper and a lower amplitude threshold limit, receiving the passband filter output signal and providing an output signal in response to a received preamplifier output signal, the comparator means output signal being "low" when receiving a preamplifier output signal having an amplitude level within the upper and the lower amplitude threshold limits of the comparator means;

switch drive means receiving the comparator means output signal, having a biased "on" and a biased "off" condition, the switch drive means being biased in the "on" condition when receiving a "low" comparator means output signal;

a threshold adjust means connected to the switch drive means receiving the switch drive means output signal in an "on" condition of the switch drive means and providing an output signal when receiving a switch drive means output signal of a predetermined minimum duration, the threshold adjust means output signal being terminated via the switch drive means output signal remaining switched to the "off" position for a predetermined minimum period of time; and

switch network means connected to the threshold adjust means having an "on" and an "off" condition, the switch network means biased in the "on" condition when receiving a threshold adjust means output signal indicating signal presence in the particular processing channel; and

feedback indicator means receiving the output signals indicative of signal presence from each of the processing channels and providing subject-perceivable feedback signals responsive thereto and indicative thereof.

5. The bio-feedback apparatus of claim 4 wherein the means in each processing channel receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel is defined further to include:

amplitude discriminator means receiving the passband filter output signal and providing an output signal substantially proportional to the amplitude of the received passband filter output signal; and

comparator controller means receiving the amplitude discriminator output signal and providing "high" output signal in response to a received amplitude discriminator output signal having a predetermined duration indicating signal presence in the processing channel, the comparator controller output signal being connected to the feedback indicator means for providing subject perceivable feedback signals in response to a comparator controller means "high" output signal.

6. The bio-feedback apparatus of claim 5 wherein the means in each processing channel receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel is defined further to include:

zero crossing detector means receiving the passband filter output signal and providing a "high" output signal in response to a negative going zero crossing of the passband filter output signal and a "low" output signal in response to a positive going zero crossing of the passband filter output signal;

tachometer network means receiving the zero crossing detector means output signal providing an output signal substantially linearly proportional to the frequency of the received zero crossing detector means output signal; and means receiving the tachometer network output signal and providing an oscillating output signal having a frequency corresponding to a multiple of the frequency of the sensed potential indicated by the tachometer network output signal; and

wherein the feedback indicator means receives the oscillating output signal corresponding to a multiple of the frequency of the sensed potential and provides a subject-perceivable feedback signal responsive thereto indicating signal presence in the particular processing channel.

7. The bio-feedback apparatus of claim 6 wherein the means in each processing channel receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel is defined further to include:

automatic gain control means receiving the amplitude discriminator output signal and the oscillating output signal corresponding to a multiple of the frequency of the sensed potential, the automatic gain control means controlling the volume of the received oscillating signal in response to the received amplitude discriminator output signal and providing an output signal corresponding to received oscillating signal having the volume thereof controlled in response to the received amplitude discriminator output signal; feedback indicator means is defined further to include an audio output indicator receiving the automatic gain control output signal and providing audible subject-perceivable feedback signal responsive thereto.

8. The bio-feedback apparatus of claim 7 wherein the means providing an oscillating output signal in response to a received tachometer network output signal is defined further to include:

non-inverting amplifier means receiving the tachometer network means output signal and providing an amplified output signal in response thereto;

unity-gain inverting amplifier means receiving the non-inverting amplifier output signal and providing an inverted output signal in response thereto;

first diode bridge means connected to and receiving the non-inverting amplifier means output signal and the unity-gain inverting amplifier means output signal;

amplifier means having an output signal connected to the first diode bridge means;

second diode bridge means connected to the amplifier means providing an output signal driving the amplifier means;

integrator amplifier means connected to the first diode bridge means and providing a triangularly shaped output signal, the integrator amplifier means output signal being connected to the amplifier means controlling the amplitude of the triangularly shaped signal produced by the integrator amplifier means; and

signal converter means receiving the integrator amplifier means output signal and providing a sine-wave shaped output signal in response thereto, the signal converter means output signal being connected to automatic gain control means and providing the oscillating signal input connected thereto.

9. The bio-feedback apparatus of claim 6 wherein the means in each processing channel receiving the passband filter output signal and providing the output signal indicating signal presence in the processing channel is defined further to include:

bandpass controller means, having a high and a low threshold setting and providing a "high" and a "low" output signal, receiving the tachometer network means output signal and providing a "low" output signal in response to a received tachometer network means output signal within the high and the low threshold setting of the bandpass controller means; and

wherein the comparator controller means receives the bandpass controller means output signal, the comparator controller providing a "high" output signal in response to a received "low" bandpass controller means output signal indicating signal presence in the processing channel within the high and the low threshold settings of the bandpass controller means output signal.

10. The bio-feedback apparatus of claim 9 wherein the tachometer network means includes: an oscillator means having an "on" and an "off" condition, the oscillator means receiving the zero crossing detector means output signal and being biased in the "on" condition in response thereto providing an oscillator means output signal; and wherein the amplitude discriminator means is defined further to include:

discriminator amplifier means receiving the passband filter means output signal and providing an amplified output signal responsive thereto;

diode means connected to and receiving the discriminator amplifier means output signal, the diode means being forward biased and conducting when receiving a positive going discriminator amplifier means output signal and being reversed biased and nonconducting when receiving a negative going discriminator amplifier means output signal;

capacitor means receiving the discriminator amplifier means output signal and being charged in response thereto in a conducting condition of the diode means;

memory capacitor means receiving the charge on the capacitor means when connected thereto;

first gate means having an opened and a closed condition connected between the capacitor means and the memory capacitor means, the first gate means receiving the oscillator output signal via the tachometer network means and being biased open in response thereto connecting the capacitor means and the memory capacitor means;

switching means connected to the capacitor means having an "on" and an "off" condition and receiving the zero crossing detector means output signal, the switching means being biased in the "on" condition in response to a received zero crossing detector means output signal in the "high" state discharging the capacitor means connected thereto; and

second gate means having an opened and a closed condition connected to the memory capacitor means and to the amplitude discriminator means, the charge on the memory capacitor means biasing the second gate means opened and providing the amplitude discriminator means output signal.

11. The bio-feedback apparatus of claim 10 wherein the tachometer network means is defined further to include:

switching means, having an "on" and an "off" condition, and receiving the tachometer oscillator means output signal and being biased "on" in response thereto;

function generator means connected to the switching means and having a portion charged in the "on" condition of the switching means, the charged portion being discharged in the "off" condition of the switching means, the function generator means providing an output signal proportional to the frequency of the sensed brain-wave potential in the discharging condition thereof;

memory capacitor means connected to the portion of the function generator charged in the "on" condition of the switch means and receiving the charge discharged from the function generator means when connected thereto; and

switching means connected to the function generator means and to the memory capacitor means, having an "on" and an "off" condition, the switching means receiving the oscillator output signal of the tachometer network means and being biased "on" in response thereto connecting the discharging function generator to the memory capacitor means.

12. The bio-feedback apparatus of claim 11 wherein the function generator means is defined further to include:

capacitor means connected to the switching means and being charged in the "on" condition of the switching means;

a resistive network bleed path connected to the capacitor means having a relatively low time constant;

a resistive network bleed path connected to the capacitor means having a relatively high time constant; and

diode means, having a forward biased and a reverse biased condition, connected to the high time constant resistive network bleed path, the capacitor means discharging through the high time constant resistive network bleed path in a forward biased condition of the diode means and through the low time constant resistive network bleed path in a reverse biased condition of the diode means, the discharging curve of the capacitor means being linearly proportional to the frequency of the sensed brain-wave potential.

13. The bio-feedback apparatus of claim 12 wherein the function generator means is defined further to include:

a resistive network bleed path connected to the capacitor means having an intermediate time constant; and

diode means connected to the intermediate time constant resistive network bleed path, the capacitor means discharging through the high and the intermediate time constant resistive networks in a forward biased condition of the diode means connected therein, the capacitor means discharging through the intermediate and the low time constant resistive networks in a reverse biased condition of the diode means connected to the high time constant resistive network, and the capacitor means discharging through the low time constant resistive network in a reverse biased condition of the two diode means.

14. The bio-feedback apparatus of claim 9 wherein the comparator controller means is defined further to include:

first comparator means, having a predetermined threshold setting, receiving the amplitude discriminator output signal and providing an output signal in a "low" state in response to a received amplitude discriminator output signal having an amplitude level exceeding the threshold setting of the first comparator means;

second comparator means receiving the first comparator means output signal and connected to the capacitor means, having a predetermined threshold setting and providing a comparator controller means output signal in a "high" state in response to the capacitor means connected thereto being discharged to a potential exceeding the threshold setting of the second comparator means; and

capacitor means connected to the second comparator means and to the bandpass controller means discharging in a "low" state of the first comparator means output signal and in a "low" state of the bandpass controller means output signal.

15. The bio-feedback apparatus of claim 14 wherein the bandpass controller means is defined further to include:

dual-comparator means, having a predetermined high and a low threshold limit, receiving the tachometer network means output signal and providing a "low" output signal when receiving a tachometer network means output signal within the high and the low threshold limit; and

gate means receiving the dual-comparator means output signal and the first comparator means output signal from the comparator controller means, the gate means being connected to the second comparator means of the comparator controller means and connecting a "low" output signal to the capacitor means when receiving a "low" dual-comparator means output signal.

16. The bio-feedback apparatus of claim 9 wherein the bandpass controller means includes: gate means inverting the bandpass controller means output signal and providing a "low" output signal in response to a received tachometer network means output signal within the high and the low threshold setting of the bandpass controller means; and wherein the feedback indicator means is defined further to include:

mixer amplifier means receiving the automatic gain control means output signals connected thereto and providing an amplified output signal responsive thereto;

relay means interposed between the mixer amplifier means and the automatic gain control means output signal of each processing channel, the relay means connecting each automatic gain control means output signal to the mixer amplifier means in an energized condition thereof; and

drive transistor means connected to the relay means having an "on" and an "off" condition and energizing the relay means in the "on" condition thereof, the drive transistor means receiving each comparator controller means output signal and each output signal of the gate means of each bandpass controller means;

diode means connected between the drive transistor means and the comparator controller means output signal and between the drive transistor means and the output signal of the gate means of each bandpass controller means, the drive transistor means being biased "on" in response to a received "high" output signal of the gate means of the bandpass controller means and a received "high" amplitude discriminator means output signal.

17. The bio-feedback apparatus of claim 9 wherein the feedback indicator means is defined further to include:

amplifier means having an "on" and an "off" condition receiving the comparator controller means output signal and being biased "on" in response to a comparator controller means output signal in the "high" state;

meter means receiving the tachometer network means output signal, providing a visual feedback signal indicating the frequency of the sensed brain-wave potential; and

relay means interposed between the tachometer network means and the meter means, connecting the tachometer network means output signal to the meter means in an energized condition thereof, the relay means connected to the amplifier means and being energized in a biased "on" condition of the amplifier means.

18. The bio-feedback apparatus of claim 5 wherein the means in each processing channel receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel is defined further to include:

data reduction controller means receiving the comparator controller means output signal indicating signal presence in the processing channel, and having a portion monitoring signal presence in the processing channel over a predetermined epoch period of time. and providing an output signal indicating the percentage of time signal presence existed in the processing channel during a subsequent predetermined period of time, an epoch period of time; and

wherein the feedback indicator is defined further to include a portion receiving the output signal indicating the percentage of time signal presence existed in the processing channel and providing a feedback indication in response thereto.

19. The bio-feedback apparatus of claim 18 wherein the data reduction means is defined further to include:

delay oscillator means generating an output signal;

analog switch means receiving the comparator controller means output signal and the delay oscillator means output signal, the analog switch means providing the delay oscillator output signal when receiving a comparator controller means output signal in a "high" state;

delay signal controller means receiving the delay oscillator means output signal via the analog switch means and recording the received delay oscillator means output signal for the predetermined epoch period of time; and

means receiving the delay signal controller means output signal and the comparator controller means output signal providing an output signal indicating the average percentage of time signal presence existed in the processing channel for the preceding predetermined epoch period of time in response to the received comparator controller means output signal and the received delay signal controller means output signal; and

wherein the feedback indicator means includes a portion receiving the output signals indicating the average percentage of time signal presence existed in each processing channel and provides a subject-perceivable feedback signal response thereto.

20. The bio-feedback apparatus of claim 19 wherein the portion of the feedback indicator means providing the output signal indicative of the average percentage of time signal presence existed in the processing channel is defined further to include:

counters for counting up to a predetermined number and counting down to zero, the counters providing a digital output signal indicative of the count registered therein and having a count-up mode, a count-down mode, and a hold mode, the counters positioned in the count-up mode in response to a received count-up signal and positioned in the count-down mode in response to a received count-down signal;

overvoltage controller means providing a "high" and "low" output signal, and having an upper and a lower threshold limit, the overvoltage controller means receiving the delay signal controller means output signal and providing a "high" output signal in response to a received delay signal controller means output signal within the upper and the lower threshold limits; and

counter controller means connected to the counters and receiving the overvoltage controller means output signal and the comparator controller output signal, the counter controller means providing an output count-up signal in response to a comparator controller means output signal in the "high" state and an overvoltage controller means output signal in the "low" stage, and an output count-down signal in response to a received comparator controller means output signal in a "low" state and an overvoltage controller means output signal in a "high" state, the digital output signals of the counters providing the output signal indicating the average percentage of time signal presence existed in the processing channel.

21. The bio-feedback apparatus of claim 20 wherein the portion of the feedback indicator means providing the output signal indicative of the average percentage of time signal presence existed in the processing channel is defined further to include:

a digital/analog converter receiving the counters output signal and providing an analog voltage output signal responsive thereto indicating the percentage of time signal presence existed in the processing channel.

22. The bio-feedback apparatus of claim 21 wherein the feedback indicator means includes:

meter drive network means receiving the digital/analog converter output signal and providing an output signal responsive thereto; and

meter means receiving the meter drive network means output signal and providing a visual feedback indicating the average percentage of time signal presence existed in the processing channel connected thereto in response to the received meter drive network output signal.

23. The bio-feedback apparatus of claim 21 defined further to include: clock pulse generator means generating a clock pulse output signal therefrom; and wherein the counters are further defined to provide output signals in the "low" state in response to a count being registered thereon and to provide output signals in the "high" state in response to a zero count being registered thereon, the counters being positioned in the count-up mode in response to a received count-up signal and a clock pulse and in the count-down mode in response to a received count-down signal and a clock pulse; and wherein the counter controller means receives the clock pulse output signal and the counters output signal, the counter controller means being defined further to include:

gate means receiving the clock pulse output signal, the comparator controller means output signal, the overvoltage controller means output signal and the counters output signals and providing an output count-up signal and a clock pulse in response to a comparator controller means output signal in the "high" state and an overvoltage controller means output signal in a "low" state, an output count-down signal and a clock pulse in response to a received comparator controller means output signal in a "low" state and an overvoltage controller means output signal in a "high" state, in response to at least one "low" counters output signal, and providing an output count-up signal and a clock pulse in response to received counters output signal in the "high" state and a received comparator means output signal in a "high" state.

24. The bio-feedback apparatus of claim 18 wherein the brain-wave indicator means includes: means detecting and sensing the brain-wave potentials produced at at least two preselected scalp sites, the brain-wave indicator means providing a controlling channel output signal indicating the sensed brain-wave potential at each scalp site; and wherein the preamplifier means receives the controlling channel output signals and provides amplified output signals responsive thereto; and wherein the bio-feedback apparatus includes: an amplitude equalizer, having a portion varying received signals about a preset amplitude reference axis, receiving and varying the amplified controlling channel output signals about the predetermined common amplitude reference axis providing the equalized amplified controlling channel output signals therefrom; and wherein processing channels include a plurality of processing channels receiving each controlling channel output signal and providing a feedback signal responsive to each received controlling channel output signal indicating signal presence in the processing channel.

25. The bio-feedback apparatus of claim 24 wherein the feedback indicator means is defined further to include:

first audio means providing subject-perceivable audible feedback signals responsive to a received signal input thereto;

second audio means providing subject-perceivable audible feedback signals responsive to a received signal input thereto; and

switch means connected to and receiving the feedback signals of each controlling channel output signal, the switch means connected to the first and the second audio means and having one switch position connecting the feedback signal from one controlling channel output signal to the first audio means and the feedback signal from one other controlling channel output signal to the second audio means, and one other switch position connecting the feedback signals from one of the controlling channel output signals to the first and the second audio means.

26. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing feedback signals in response thereto, the apparatus comprising:

a brain-wave indicator detecting and sensing the brain-wave potentials, and providing an output signal responsive thereto;

a processing channel receiving the brain-wave indicator output signal and providing a feedback signal responsive thereto, the processing channel comprising:

frequency discriminator means having a predetermined passband, receiving the brain-wave indicator output signals and providing an output signal responsive to the frequency component of the received signal within the passband of the frequency discriminator means;

means receiving the frequency discriminator means output signal and providing an output signal indicating signal presence in the processing channels;

a data reduction controller means receiving the output signal indicating signal presence in the processing channel and providing an output signal indicating the percentage of time signal presence exists in the processing channel for a subsequent predetermined epoch period of time, the data reduction controller means including:

delay oscillator means generating an output signal;

analog switch means receiving the output signal indicating signal presence in the processing channel and the delay oscillator means output signal, the analog switch means providing the delay oscillator means output signal in response to a received output signal indicating signal presence in the processing channel;

delay signal controller means receiving the delay oscillator means output signal from the analog switch means and recording the received delay oscillator means output signal for the predetermined epoch period of time and providing an output signal responsive thereto; and

means receiving the delay signal controller means output signal indicating signal presence in the processing channel during the predetermined epoch period of time and providing an output signal indicating the average percentage of time signal presence existed in the processing channel for the predetermined epoch period of time, including:

counters for counting up to a predetermined number and counting down to zero, the counters providing a digital output signal indicating the count registered therein and having a count-up mode, a count-down mode, a hold mode, the counters being in the count-up mode when receiving a received count-up signal and being in the count-down mode when receiving a count-down signal;

overvoltage controller means providing a "high" and a "low" output signal, and having a predetermined upper and a lower threshold limit, the overvoltage controller means receiving the delay signal controller means output signal and providing a "low" output signal in response to a received delay signal controller means output signal within the upper and the lower threshold limits of the overvoltage controller means; and

counter controller means connected to the counters and receiving the overvoltage controller means output signal indicative of signal presence in the processing channel, the counter controller means providing an output count-up signal when receiving an over-voltage controller means output signal in the "low" state indicating signal presence in the processing channel, and an output count-down signal when receiving an overvoltage controller means output signal in a "high" state, the count registered in the counters indicating the percentage of time signal presence existed in the processing channel during the predetermined epoch period of time; and

feedback indicator means receiving the output signal indicating the percentage of time signal presence existed in the processing channel and providing a subject-perceivable feedback signal responsive thereto.

27. The bio-feedback apparatus of claim 26 wherein the means providing the output signal indicating the average percentage of time signal presence existed in the processing channel is defined further to include:

a digital/analog converter receiving the counters output signal and providing an analog voltage output signal responsive thereto indicating the percentage of time signal presence existed in the processing channel.

28. The bio-feedback apparatus of claim 27 defined further to include: clock pulse generator means generating a clock pulse output signal therefrom: and wherein the counters are further defined to provide output signals in the "low" state in response to a count being registered thereon and to provide output signals in the "high" state in response to a zero count being registered thereon, the counters being positioned in the count-up mode in response to a received count-up signal and a clock pulse and in the count-down mode in response to a received count-down signal and a clock pulse; and wherein the counter controller means receives the clock pulse output signal and the counters output signal, the counter controller means being defined further to include:

gate means receiving the clock pulse output signal, the comparator controller means output signal, the overvoltage controller means output signal and the counters output signals and providing an output count-up signal and a clock pulse in response to an output signal indicative of signal presence in the processing channel and an overvoltage controller means output signal in a "low" state, an output count-down signal and a clock pulse in response to a received overvoltage controller means output signal in a "high" state, in response to at least one "low" counters output signal, and providing an output count-up signal and a clock pulse in response to a received output signal indicative of signal presence in the processing channel, in response to received counters output signals in the "high" state.

29. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing feedback signals in response thereto, the apparatus comprising:

brain-wave indicator means detecting and sensing the brain-wave potentials and providing an output signal responsive thereto;

preamplifier means receiving the brain-wave indicator means output signal and providing an amplified output signal responsive thereto;

passband filter means, having a predetermined passband, receiving the preamplifier output signal and providing an output signal responsive to a frequency component of the received signal within the filter means passband;

zero crossing detector means receiving the passband filter means output signal and providing a "high" output signal in response to a positive going zero crossing of the passband filter means output signal and a "low" output signal in response to a negative going zero crossing of the passband filter means output signal;

tachometer network means receiving the zero crossing detector means output signal providing an output signal proportional to the frequency of the received zero crossing detector means output signal;

means receiving the tachometer network means output signal and providing an oscillating output signal having a frequency corresponding to a multiple of the frequency of the sensed potential indicated by the tachometer network means output signal;

amplitude discriminator means receiving the passband filter means output signal and providing an output signal substantially proportional to the amplitude of the received passband filter means output signal;

comparator controller means receiving the amplitude discriminator means output signal and providing "high" output signal in response to a received amplitude discriminator means output signal having a predetermined minimum duration, in one position thereof;

bandpass controller means having a predetermined high and a predetermined low threshold setting and providing a "high" and a "low" output signal, receiving the tachometer network means output signal and providing a "low" output signal in response to a received tachometer network means output signal within the high and the low threshold settings of the bandpass controller means, the bandpass controller means output signal connected to the comparator controller means and the comparator controller means providing the output signal therefrom in the "high" state of the bandpass controller means output signal; and

feedback indicator means connected to the comparator controller means receiving the comparator controller means output signal and providing subject-perceivable feedback signals in response to a received "high" comparator controller means output signal.

30. The bio-feedback apparatus of claim 29 wherein the tachometer network means includes: an oscillator means having an "on" and an "off" condition, the oscillator means receiving the zero crossing detector means output signal and being biased in the "on" condition in response thereto providing an oscillator means output signal; and wherein the amplitude discriminator means is defined further to include:

discriminator amplifier means receiving the passband filter means output signal and providing an amplified output signal responsive thereto;

diode means, having a forward biased and a reverse biased condition, connected to and receiving the discriminator amplifier means output signal, the diode means being forward biased and conducting when receiving a positive going discriminator amplifier means output signal and being reversed biased and nonconducting when receiving a negative going discriminator amplifier means output signal;

capacitor means receiving the discriminator amplifier means output signal and being charged in response thereto in a conducting condition of the diode means;

memory capacitor means receiving the charge on the capacitor means when connected thereto;

first gate means having an opened and a closed condition connected between the capacitor means and the memory capacitor means, the first gate means receiving the oscillator output signal via the tachometer network means and being biased open in response thereto connecting the capacitor means and the memory capacitor means;

switching means connected to the capacitor means having an "on" and an "off" condition and receiving the zero crossing detector means output signal, the switching means being biased in the "on" condition in response to a received zero crossing detector means output signal in the "high" state discharging the capacitor means connected thereto; and

second gate means having an opened and a closed condition connected to the memory capacitor means and to the amplitude discriminator means, the charge on the memory capacitor means biasing the second gate means opened and providing the amplitude discriminator means output signal.

31. The bio-feedback apparatus of claim 30 wherein the tachometer network means includes:

switching means, having an "on" and an "off" condition, and receiving the tachometer oscillator means output signal and being biased "on" in response thereto;

function generator means connected to the switching means and having a portion charged in the "on" condition of the switching means, the charged portion being discharged in the "off" condition of the switching means, the function generator means providing an output signal proportional to the frequency of the sensed brain-wave potential in the discharging condition thereof;

memory capacitor means connected to the portion fo the function generator charged in the "on" condition of the switch means and receiving the charge discharged from the function generator means when connected thereto; and

switching means connected to the function generator means and to the memory capacitor means, having an "on" and an "off" condition, the switching means receiving the oscillator means output signal of the tachometer network means and being biased "on" in response thereto connecting the discharging function generator to the memory capacitor means.

32. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing feedback signals in response thereto, the apparatus comprising:

brain-wave indicator means detecting and sensing the brain-wave potentials at two preselected sites, and providing a controlling channel output signal indicating the sensed brain-wave potential at each site;

preamplifier means receiving the controlling channel output signals and providing amplified output signals responsive thereto;

a plurality of processing channels, some of the processing channels receiving one of the controlling channel output signals and providing a feedback signal responsive thereto, some of the other processing channels receiving one other of the controlling channel output signals and providing a feedback signal responsive thereto, each of the processing channels comprising:

frequency discriminator means, having a predetermined passband, receiving the preamplifier output signal and providing an output signal responsive to a predetermined frequency component of the received preamplifier output signal having a frequency within the passband of the frequency discriminator means; and

means receiving the frequency discriminator means output signal and providing an output signal indicating signal presence in the processing channel, comprising:

first audio means providing subject-perceivable audible feedback signals responsive to a received signal input thereto;

second audio means providing subject-perceivable audible feedback signals responsive to a received signal input thereto; and

switch means receiving the feedback signals of each controlling channel output signal and connected to the first and the second audio means, the switch means having one switch condition connecting the feedback signal from one controlling channel output signal to the first audio means and the feedback signal from one other controlling channel output signal to the second audio means, and one other switch condition connecting the feedback signals from one of the controlling channel output signals to the first and the second audio means.