U.S. patent number 3,810,106 [Application Number 05/295,234] was granted by the patent office on 1974-05-07 for system for storing tone patterns for audible retrieval.
This patent grant is currently assigned to APM Corporation. Invention is credited to Mitchell A. Cotter, Bernard David Nadler.
United States Patent |
3,810,106 |
Nadler , et al. |
May 7, 1974 |
SYSTEM FOR STORING TONE PATTERNS FOR AUDIBLE RETRIEVAL
Abstract
A system of storing information as a purality of parallel,
finite length tracks, each track constitiuting a discrete tone
pattern, and means for retrieving said tone patterns by orthogonal
scanning of said tracks using a single scanning device, whereby the
entire field of stored information is substantially simultaneously
available for reproduction. The system is particularly suited for
audible retrieval, with disclosed application to voice
reproduction, vocoders, and electronic keyboard instruments.
Inventors: |
Nadler; Bernard David (Bayside,
NY), Cotter; Mitchell A. (Henry Hudson Parkway, NY) |
Assignee: |
APM Corporation (Englewood,
NJ)
|
Family
ID: |
23136823 |
Appl.
No.: |
05/295,234 |
Filed: |
October 5, 1972 |
Current U.S.
Class: |
434/178; 84/609;
369/121; 984/358; 84/649; 369/97; 984/391; G9B/7.004 |
Current CPC
Class: |
G10L
13/06 (20130101); G10H 3/06 (20130101); G11B
7/0033 (20130101); G10H 7/02 (20130101); G09B
5/04 (20130101) |
Current International
Class: |
G10H
7/02 (20060101); G10L 13/00 (20060101); G10H
3/06 (20060101); G09B 5/00 (20060101); G10L
13/06 (20060101); G10H 3/00 (20060101); G09B
5/04 (20060101); G11B 7/00 (20060101); G11B
7/0033 (20060101); G06f 003/00 (); G06f 007/00 ();
G11b 007/00 () |
Field of
Search: |
;179/1SA,1.2MD,1.3B,1.3T
;84/1.01,1.03,1.28 ;178/6.6FS,6.7R ;340/173LM,173LT,172.5
;235/61.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Henon; Paul J.
Assistant Examiner: Thomas; James D.
Attorney, Agent or Firm: Temko; Charles E.
Claims
1. Structure for storing and retrieving data comprising a
predetermined data record containing a denumerable number of data
channels, and means for reading by sampling in cycles of a time
sequence each channel of such data, each channel being of
substantially the same finite length, and so disposed that the same
relatively positioned fractional element of each channel length is
sampled in one complete cycle of such time sequence, said reading
means shifting progressively the cycles of sampling over at least
part of the entire length of the finite length channels, thereby
manifesting at the output of said reading means a separable set of
samples representing a continuous set covering the total of all
data contained in the portion of the record sampled, said reading
means performing within one time frame a complete set of cycles of
sampling which covers the sampled length of a channel; and means
for selecting from among the sampled set within one complete set of
cycles those sample elements that represent continuously at least a
portion of one of the channels of the data record, thereby allowing
the reconstruction of the desired channel to
2. A system for storage and retrieval of encoded data comprising a
plurality of elongated two dimensional storage mediums, each having
a principal longitudinal axis of finite length, said mediums being
positioned in mutually juxtaposed relation with said longitudinal
axes mutually parallel, each medium storing at least a single item
of data; and playback multiplexer means scanning said plurality of
mediums in a direction substantially perpendicular to that of said
principal axes to provide a sampling of all of said mediums,
interleaving said samples in time and placing them within one
channel in such manner that they appear
3. Structure in accordance with claim 2, in which said playback
means includes a permanent storage medium, a scanning energy
source, sensor collector means receiving said energy from said
source, and transducer means connected to said sensor collector
means for producing an audible output.
Description
This invention relates generally to the field of data storage, and
more particularly to the storage and retrieval of tone patterns for
audible reproduction. While the possible uses of the invention have
application in many areas, the invention has particular application
to the field of reproduction of a stored spoken vocabulary, and
musical instruments, such as electronic organs and similar keyboard
control devices.
BRIEF DESCRIPTION OF THE PRIOR ART
In prior art devices, audible sounds are normally stored in
parallel tracks upon rotating drums or other moving storage
mediums, and a separate pickup or other retrieval device is used
for each track. Given consideration of space and cost, most audible
retrieval devices in the prior art are limited to relatively small
vocabularies of the order of less than 50 words, and seldom exceed
100 words.
The storage of musical sounds has largely been confined to
continuous single tracks, typified by phonograph records and tapes,
and while the use of recorded sound to provide a tone source for
musical instruments is not entirely unknown, prior art embodiments
have been so limited with respect to response time, tone quality
and available tonal range as to be lacking in serious utility.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
Briefly stated, the invention contemplates the provision of a
generally rectangularly shaped storage record having a large
plurality of recorded sound tracks of finite length arranged in
parallel juxtaposed position upon the record. This record is
scanned orthogonally at very high speed in raster-like fashion such
that each deflection of scanning being perpendicular to the axis of
the sound tracks crosses all of the tracks, thus potentially
reading all of the information contained in the record to make the
same available for retrieval over a very short period of time.
Scanning is performed using a laser beam, and electro optical
reproduction is performed at far greater than real time output
rates. Analog retrieved signals are converted to digital values,
and are rapidly stored using one or more storage registers which
are then unloaded at relatively slower intervals, the retrieved
signals then being again converted to analog values, suitably
modified, and amplified, and transduced.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, to which reference will be made in the
specification, similar reference characters have been employed to
designate corresponding parts throughout the several views.
FIG. 1 is a schematic block diagram showing a first embodiment of
the invention.
FIG. 2 is a fragmentary schematic view showing certain aspects of a
finite length record forming a part of the embodiment.
FIG. 3 is an enlarged fragmentary view corresponding to the upper
left hand portion of FIG. 2.
FIG. 4 is a still further enlarged fragmentary view showing three
recorded tracks which form part of the finite length record.
FIG. 5 is an enlarged fragmentary view showing certain other
aspects of the record; e. g., scanning of the same.
FIG. 6 is a schematic view of the laser and laser drive system
forming the record scan elements of the embodiment.
FIG. 7 is a fragmentary graphic representation of three orthogonal
scans of a finite length track comprising a part of the record.
FIG. 8 is a graphic representation of the nature of signals of
positive and negative character generated by the scanning
operations shown in FIG. 7.
FIGS. 9a and 9b are a block diagram showing the processing of
signals shown in FIG. 8.
FIG. 10 is a schematic diagram of a tunnel diode flip-flop forming
a part of the embodiment.
FIG. 11 is a schematic block diagram showing the loading and
unloading of processed data in alternate fashion of first and
second data shift registers.
FIG. 12 is a block diagram showing for the track selection memory
the operation of shift registers.
DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT
Before entering into a detailed consideration of the first
embodiment of the invention, which relates to an electronic organ,
a brief review of the state of the electronic organ art is
considered apposite.
Over the past 35 years various attempts have been made to create
organs suitable for institutional and home use at a cost far less
than that of conventional pipe organs. The latter have always been
essentially hand built, and the nature of construction of the same
does not lend itself to mass production. The earliest electric
organs were simple variants of the old-fashioned reed organ, in
which air is circulated over reeds to produce a relatively faint
tone. This tone is electrically amplified for volume and modified
for vibrato and tremulo effects, but essentially the tone produced
is that of the vibrating reed initially generating the tone, and
thus the tonal range of such instruments is very limited.
Approximately in 1936, a second advance in the art was created by
the Hammond Organ Company in which tone generation was accomplished
by providing a rotating shaft having a large plurality of tone
wheels, the shaft being driven by a synchronous motor. The
peripheries of the tone wheels are modified so as to permit the
generation of tone at proper frequency when the shaft is rotated at
a predetermined rate. This organ system provided an advantage in
that vacuum tubes need only be required for amplification stages of
reproduction, and while the tone produced is quite pleasing, it
does not even approximate the tone of a fine pipe organ. While such
instruments are in widespread use at the present time, they are
suitable principally for the performance of non-classical and
non-liturgical literature.
With the extended development of transistors to replace vacuum
tubes, the art progressed to the use of individual circuits for
each desired tonal frequency, and the quality of tone generation
remarkably improved to a point where the tone obtained from better
organs using independent electronic tone generation is quite
acceptable for serious musical performances. It has been possible
to duplicate typical pipe organ effects, such as chiff, as well as
the tone decay typically experienced with organs using a so-called
tracker action in which the keys are directly mechanically
connected to the valves supplying air from a windchest to a pipe.
Such electronic organs are relatively costly, and truly fine
instruments of this type rival in cost that of fine pipe
organs.
The first embodiment of the invention contemplates the provision of
an electronic organ capable of producing pipe organ tones, not by
electronic tone generation, but by reproducing previously recorded
tone patterns obtained from a pipe organ, or other desired source.
Each pitch of a desired stop or mixture recorded from the pipe
organ is stored as a separate track, including at the terminal
portions thereof various forms of ictus and decay, as well as a
medial portion of continuous tone using the above described
multiplexing retrieval technique. Upon a call from the keyboard,
successive portions of the required recorded tracks are sampled,
and the corresponding analog voltage samples are obtained
optically. These voltages are digitized, and where several tone
patterns are simultaneously called for, the corresponding digital
voltages are summed and transferred to a storage register. The
storage register is unloaded at real time rates, the sampled
voltages being subsequently converted again to analog form for
subsequent processing, amplification and replay via a suitable
transducer.
With the foregoing in view, reference may now be made to the
drawings, in which, in accordance with the first embodiment of the
invention, the device, generally indicated by reference character
10, comprises broadly: a keyboard element 11, a stop and piston
programming element 12, a main computer element 13 including a real
time clock 14, a scan period clock generator 15, a laser element
16, and related laser scanner drive system 16a, a selectively
replaceable storage record 17, acousto-optical deflecting means 18,
a signal processing amplifier 19, sampling gating means 20, pulse
modulation means 21, a summing amplifier 22, an analog to digital
converter 23, time conversion system means 24 including digital
memories 25 and 26, a digital to analog converter 27, audio power
amplifier means 28 and speakers 29.
The keyboard element 11 and stop and piston programming element 12
may resemble those of existing electronic organs, the former
including one or more keyboards of the usual 44 or 61 note content,
each key closing an electrical circuit signalling the main computer
element. The stop and piston programming element externally
resembles those of existing electronic organs, although it may be
mentioned that by virtue of the selectable replacability of the
storage record 17, changes in selected stops and mixtures can be
also accomplished by changing the record which in effect changes
the stop compliment of the instrument.
The main computer element 13 includes a control link 33 to a pair
of track select memories 34 and 35, the operation of which will be
more fully described hereinafter. A control link 36 interconnects
with the time conversion system 24.
A discussion of the laser 16 and its drive system 16a is preferably
deferred to a description of the record 17. The record 17, as has
been mentioned is in analog form, and is of a size which permits
convenient replacement. In preferred form, it consists of one or
more high resolution recording plates of glass, the operative
surface of which is coated with a thin film of etchable metal, such
as chromium. Plates of this general type are presently commercially
available from Eastman Kodak Company. Referring to FIG. 2, a
recorded area 39 is bounded by an upper edge 40, a lower edge 41,
as well as left and right side edges 42 and 43, respectively. The
recorded area 39 is divided into 30 vertical sectors or frames 44
four inches in height, and 0.200 inches in width. Each sector is
separated from the adjoining sector by a sector synchronization
band 45 of 0.010 inches, so that the total width of all 30 bands
and sectors is 6.600 inches. A vertical start synchronization band
46a is 0.100 inches in height.
Extending horizontally over the 30 data sectors are 1,000 sound
tracks generally indicated by reference character 47, each of total
height of 100 microns, each track representing a distinct pitch and
tonal quality. The 1,000 tracks will serve to record the tones of
20 ranks of pipes each with capacity of 50 notes per rank. It will
be understood that other distribution may be employed if desired.
These tones are pre-recorded onto a master record, and duplicates
are prepared by well-known photo etching processes. It is assumed
that in some cases several "attack" periods and possibly several
"decay" periods are recorded on each track at each end of a steady
state tone. In real time length, each track is given one second
duration. The steady state tone is sustained indefinitely by the
continued contiguous repetition of the steady state segment. During
operation, the entire group of 30 sectors is scanned at a rate 30
times the real time rate, i.e., 33 milliseconds non-real time for
each frame. The system divides time into 33 millisecond real time
intervals, and interprets the keyboard commands as simultaneous if
they are closer together than 33 milliseconds. All events are then
positioned into such sublimits of time, this period being
sufficiently short to avoid any subjective restrictions, and
facilitates the conversion to real time playback of any possible
note combinations of attack, decay or voicing. The tones once
available in real time may also be tone modified by signal
processing to provide a number of other "stop effects." The system
is oriented, however, to provide a large range from the memory
record medium alone.
It will be apparent that the 33 millisecond period is not
invariable, and may be modified to suit the requirements of future
needs or other real time conversion.
As will be more fully apparent hereinafter, the purpose of grouping
into sectors is twofold. Firstly, since the entire record is
scanned in 33 milliseconds actual time, only 33 milliseconds worth
of information need be provided to the memory for the next 33
milliseconds output, and the scan will make available any
information that will be required for the next 33 milliseconds
output during the readout of that memory list. There are two memory
shift registers 26 and 27, so that one may load while the other is
read out. Secondly, since the data is digitized for each vertical
scan, slice by slice through the 1,000 tracks, and through sector
by sector, each slice is integrated, digitized, and that sample set
considered as the sampled value of the total of events that are
called forth in that slice of time. The length of memory for each
register is equivalent to the total slices in one sector. However,
the memory is cyclically unloaded and reloaded with each succeeding
sector scan, so that any additional track segment which has been
commanded will be additionally loaded as though it were recorded
coincident with the previously sampled track segments. Thus, any of
the sector elements may couple with any other sector elements, to
provide complete musical flexibility to play any combination of
tones at any time, including all notes together.
To avoid noise problems of analog light magnitude (variable area or
density), present when very fast scans are employed, a phase
modulation scheme is employed. This system permits superior
signal-to-noise performance, and the very high density of data that
a variable area metal-clad grainless plate provides.
FIGS. 3 and 4 illustrate the track detail. Each track is bounded by
a rectilinear upper edge 48 and a modulated lower edge 49 enclosing
a reflective area 50 and an adjacent open area 51. Two photo
detectors are used, one sensing the transmission of the laser beam
through the plate, and the other the reflection of it from the
bright metal-clad face of the plate in the areas opaque to
transmission. The start of a reflection (or scatter) pulse is
employed to set the pulse width modulator means 21, and the start
of a transmitted light pulse is used to stop the pulse width
discriminator period. The variable pulse-width is used to open and
close an ultrafast constant current gate to a fast integrator which
integrates all of the samples of all the tracks that are to be used
during a single slice. This pattern remains as required during one
sector of 1,000 slices for the system illustrated. Thus, it is the
width of metal from the rectilinear edge 48 to the variable edge 49
which carries the modulation. Since the track samples range in
width from 100 picoseconds to 900 picoseconds and recur with a 1
nanosecond spacing, performing the summing of coincidence signals
at this point avoids the need to further handle these very short
pulses. The pulse width discriminator gates employ, for example,
tunnel diodes which may be even faster than required in this
design, and use a novel manner of allowing the current output to be
bipolar so that each track has its zero signal level (50 percent)
sensed as a zero net current to the integrator (see FIG. 7). Thus,
the signals may simply be added without any variable bias effects
that either a variable area or variable density system would
generate when different numbers of tracks are combined. Either of
such tracks are an analog transmission modulation system, and so
the static transmission would vary with the number of tracks and
since there is no negative light transmission, some balance or
other similar scheme would be required to serve in the analog
amplitude domain at these very high sampling speeds. Balancing and
digital processing of very high speed pulses are both very
difficult to perform. In the present construction (see FIG. 7) use
is made of the relation of the timing between the backscatter pulse
edge and the transmitted pulse edge to differentially operate a
bipolar integration of the pulse widths.
For example, in that portion designated slice A, .A1 designates the
commencement of the backscatter pulse, .A2 designates the
commencement of the transmitted pulse, and .A3 the commencement of
the next backscatter pulse on an adjacent track.
The pulse corresponding to .A1 starts positive current integration.
.A2 stops positive current integration and starts negative current
integration. Negative current integration is stopped by the delayed
arrival of the back-scatter pulse from .A1. Thus, only the leading
edges of the pulses are required to effect a biasless detection of
the modulated displacement of the opaque edge. In the present
construction, since the scanning speed is closely locked to the
scan and a stable time base, the system operates well without
severe analog demands. The low frequency noise of the laser is
eliminated and the system operates with greater than 50db
signal-to-noise ratio at the stated conditions. The laser 16 may be
of a type known in the art. A suitable model is currently marketed
by Radio Corporation of America, Camden, N. J. under No. L15429 and
is of helium-neon short path coaxial 14 centimeter gas type having
a doppler width of approximately 4GHz and an output of a few
milliwatts this laser is described in greater detail in R.C.A.
Publication No. TL-4001, dated Feb, 1972, under the title GAS
LASERS. The laser drive system 16a includes a rear mirror 57, an
ADP mode lock control 58, a spatial filter 59, and a 2cm etalon
filter 60, the above system having an exit yield of greater than
2.times.10.sup.15 photon/second. This yield is focused by a lens
system 61 which transmits the light output to the acoustooptic
deflector means 18. The system 18 may be of a LiNbO.sub.3 or
PbMo0.sub.4 type, operating in the 1 GH.sub.Z region. Frequency
modulation of drive yields a Bragg angle modulation of over
6.degree.. (Footnote 1)(Footnote 1: See Guidlines For The Selection
Of Acoustooptic Materials, Douglas A. Pinnow, IEEE Journal Of
Quantum Electronics, Volume QE-6, No. 4, Apr. 1970)
Light emanating from the y-deflecting means 18 enters an exit lens
system 63 to impinge upon reflecting mirrors 64 and 65.
X-deflection is accomplished by a rotating prism system 66 which
passes light through an apertured mirror 67, and the record 17. The
transmitted light falls upon a second apertured mirror 70 which
reflects light back to a Cassegranian mirror 70a and then upon the
transmitted light sensor 71. Reflected light passes to the
reflected light sensor 73 by the first apertured mirror 67. The
electrical output of the sensors passes to the signal processing
amplifer 19.
The signal processing amplifiers 19, sampling gates 20 and pulse
width modulation discriminator 21 as well as the summing amplifier
22 or integrator are best understood from a consideration of FIGS.
9a, 9b and 10. The two principal signal processing functions
performed are to amplify and to feed the transversal filter with
the outputs of the photo sensors. These photo sensors will either
be photo multiplier tubes or fast solid state diodes of light
sensitive type. As is known in the art, these devices have an
acceptable rise time, but a much slower fall time, and the signal
amplifiers include a transversal filter to shape a narrow pulse
from the rise portion of the light pulse. Typical slices of the
scanning light beam are illustrated in FIG. 8, and after shaping,
the positive signal represents the metal coated reflected zone, and
the negative signal the transmitted light zone. It is to be noted
that a 50 percent area (i.e., no signal) produces zero output. The
signals may therefore be summed without bias errors, and the
integrator therefore gives the sum total algebraic value of all
sampled signals in a single slice.
After signal processing, the signals are fed to delay
match-adjusting devices 87 and 88, and subsequently to Schottky
diode gates 89 and 90. The leading edge of the backscatter pulse as
shaped into a pulse by the signal processing amplifier and
transversal filter feeds through the delay-adjust and sampling gate
system. The positive current gate tunnel diode flip-flop 97a is set
by this pulse. It is reset by the transmitted light pulse which is
similarly obtained. This pulse also sets the negative gate tunnel
diode flip-flop 98a. Flip-flop flop 98a is reset by the delayed
arrival of the prior backscatter pulse through delay line 94. The
output of the flip-flops is used to control current gates 97 and 98
which alternately charge the integrator 22. The output of the
integrator 22 is fed to the sample and hold device 22a which feeds
the analog to digital converter 23 which is of a 12 bit type (sign
plus 11 bits), the converter loading the digital memories 26 and 27
once per slice.
Referring to FIG. 11, the time conversion system 24 is illustrated
in greater detail. The function of this structure is to enable
digital information to alternately flow into one or another of the
two memories, so that one may be loaded, while the other is
unloaded to create a continuous flow of digital information. Each
set of shift registers is loaded with data from the analog to
digital converter which passes through a 16 bit plus sign digital
adder. This adder permits the addition of later selected track
segments to be added to the segments previously sampled without
loss or disturbance of data. The memory shift register set thus is
unloading the just previously loaded sector data during each
subsequent sector scan. The adder accomplishes the simple addition
of later selected data permitting the coincident reproduction of
data from any sectors. After 30 such loading cycles, the shift
register set is transferred during the synchronizing interval from
load operation at sampling rate to unload operation at real time
clock rate by the gates 108-109, load clock gates 112-a and 112b
and readout clock gates 113a and 113b. Each of the 18 parellel
registers in both A and B sets are 1,001 bits long. The load clock
is synchronized to the fast scan at a 1 nanosecond rate. Unloading
is 30 times slower and is controlled by a readout clock 113
operating at real time, i.e., a 33 microsecond rate. Thus, all data
which has accumulated during the 33 millisecond period during which
the register was loaded, is simultaneously available at readout
time. The unload gates 114 and 115 are also controlled by memory
control logic which also controls the sync and section 1 inhibit
gates with 116 and 117, which control the digital adder 107. The
shift register sets each have one register that has a one bit index
value to mark the start of the 1,000 bit cycle. This index register
acts as a cycle counter. The memories are cleared by the adder
during the first sector operation because of the presence of the
sector 1 inhibit pulse which effectively adds only zero to the new
input data.
Referring to FIG. 12, the track-select system 30 which controls the
sampling gate means 20 is illustrated in greater detail. The
track-select memories are duals, one reading out to drive the
sampling gates at speeded up scan rate of 952 picoseconds per
track, while the other loads the 1,000 track select bits during the
1.05 milliseconds scan time of the current sector. The track-select
data requires revision only once per sector. The load time is
therefore a relatively simple matter for computer control. The fast
gate information is derived from ten lower registers by a delay
line driven by ORing fast AND gates to drive the sampling pulse
amplifier. FIG. 12 illustrates one of two identical track-select
memories, both of which receive a 952 picosecond clock gated out
sync pulse, generally indicated by reference character 200. This
pulse feeds a divide by 10 scaler and 1 nanosecond pulse generator
201. The output of 1 nanosecond pulses is successively delayed at
each fast shift register readout gate 125 by a 952 picosecond delay
member 122, so that each fast shift register 124 is gated out in
succession. The delay elements accomplish two functions. The first
above described function appropriately delays the readout of the
slower than desirable fast shift registers 124. This permits memory
control of the fast sampling operation to select tracks. The slower
memories are started in shift mode by the next delayed 1 nanosecond
pulse via gate 123. The ORed fast current mode AND gates 125
receive pulses from the registers and gate them to an amplifier 126
to operate the sampling gating means 20. Data-in gate 127 is
controlled from the computer 13, and a shift clock 128 is connected
in parallel with the read gate 123 for entry of data from computer
control during the relatively long 1 millisecond interval required
for a sector scan, by the write in gate.
Referring again to FIG. 1, the output of the digital to analog
converter 27 passes to the audio power amplifier 28 which will
normally include a volume control operated by the swell pedal of
the organ. The speakers 29 may be of conventional type, including
rotary driven types commonly used in the electronic organ art.
To recapitulate, each track contains a real time length of 990
milliseconds. There are 30 cycles of complete scan of the record
medium for a complete readout of the entire track length. Each of
the 30 cycles requires 33 milliseconds actual time.
During a single pulse width modulation scan, each single track is
scanned for 952 picoseconds, and each vertical scan or slice is
1.00 microseconds. Thus each of the 30 sectors is sliced 1,000
times in the 1.00 millisecond scan time for that sector. Sectors
are separated by a sync period of 0.05 milliseconds equal to 50
slices. Thirty sectors make up one complete record, with 750
microsecond start sync and 750 microsecond stop sync added to the
31.5 millisecond scan time to make a total of 33 milliseconds for
the total record. Thus, 30 of these speeded up scans of the total
record are able to provide readout of the contents of one full
track length in 990 milliseconds.
A single slice scan time equals 1 microsecond, and 1,000 such
slices are completed as the beam transverses a single sector. All
pulse width modulation current pulses from selected tracks are
being integrated during each single slice, and the integrated value
from the previous slice is simultaneously being digitized by the 12
bit analog to digital convertor and stored in the data memory
sector then in the load mode. During each sector scan, one of the
two track-select memories is read to gate the desired tracks, and
the other is loaded with the select data for the next sector to be
scanned. The first sector selection is loading during both long 750
microsecond sync periods.
During this period, signal memory A (digital 1,000 bits) may be
reading out in real time while the other memory (section B) is
being loaded by the then active scan of the data record. Note that
each sector of 1,000 bits additively reloads into the memory the
selected tracks so that the readout of the memory can contain
elements of sectors from any portion of the data record. This
permits the selection of desired ictus and tone decay which may be
contained in the first two or three sectors and the last two or
three sectors.
The operation of the tunnel diodes 97a and 98a can be understood by
the drawing in FIG. 10. Tunnel diodes TD-1 and TD-3 are of
Gallium-arsenide type in order to provide sufficient switching
voltage to operate current gate 97. Resistor 143 is chosen such
that with potential e+ applied to the combination of tunnel diode
and inductors 140 and 141 only one of the two diodes is turned on
and the current flowing is below the peak value for switching of
the tunnel diodes. Inducter 142 and resistor 143 are chosen to
permit the application of a trigger pulse at point P1 through
capacitor 144. This trigger pulse causes the peak current in the
unswitched diode to exceed its trigger point and hence switches it
into the onstate thus extinguishing the operation of the on diode
from its forward potential. The operation of this circuit is well
known in the art.
The tunnel diode flip-flop is designed for the purpose of operating
current gate 97 and in a complementary manner current gate 98. Gate
97 is composed of resistor 150 and inductor 151 together with
Shottke diodes D1 and D3. Current gate 97 operates by sending
current from i+ through either diode D1 or D3 depending upon the
potential of the cathode of D1. If D1's potential on the cathode
exceeds that of e.g. the summing junction of the integrator, then
all the current is shunted into D3 and thereby into the integrator.
When D1's cathode is more than 3/10 of a volt below the potential
on e.g. diode D3 is effectively backbiased and all the current is
shunted through diode D1 to be sunk in the output of tunnel diode
flip-flop 97a in TD-3. It should be noted that the current i+ is
not altered by the effect of the switching action. Thus it is that
the current fed to the integrator is determined by the set value of
i+ and the width of the onswitched condition of tunnel diode TD-3.
The negative polarity of summing junction current is introduced to
the integrator in like fashion by means of tunnel diode flip-flop
98a and current gate 98. Both of these are arranged with the
polarities of anode and cathode inverted and operate in
corresponding manner to provide a switching function for the
negative current. Integrator 160 consists of amplifier and
capacitor 161 the combination designed to maintain potential e.g.
always at ground and to represent by its output potential the
magnitude of current introduced into the summing junction. This
integrator operates during one slice to integrate the total value
of all switched current pulses during that slice and is reset to
zero by the action of an output clamp circuit 163 and an input
clamp circuit 164 composed of four diodes. Clamp 164 operates with
a positive current pulse to provide a high current reset of the
capacitor and amplifier to zero. It is of a well known type and
need not further be described here. The integrator 22 consists of
an amplifier 160 and a feedback capacitor 161 designed to maintain
potential e.g. always at ground. This integrator operates during
one slice to integrate all the current width pulse applied to it,
from the tunnel diode flip-flop 97a and 98a. It is reset to ground
after the sample hold circuit has determined the final value of
integrated current pulses by means of a clamp circuit on the output
163 and an input clamp circuit composed of four diodes. The input
clamp circuit 164 controls the four diodes. Clamp circuit 164 is of
a well known type designed to operate upon positive current flow in
which the diodes force discharge of capacitor and resetting
potential to ground. It need not be described further in detail
here.
We wish it to be understood that we do not consider the invention
limited to the precise details of structure shown and set forth in
this specification, for obvious modifications will occur to those
skilled in the art to which the invention pertains.
* * * * *