U.S. patent number 3,771,406 [Application Number 05/170,489] was granted by the patent office on 1973-11-13 for musical instrument with digital data handling system and lighting display.
This patent grant is currently assigned to The Wurlitzer Company. Invention is credited to Robert W. Wheelwright.
United States Patent |
3,771,406 |
Wheelwright |
November 13, 1973 |
MUSICAL INSTRUMENT WITH DIGITAL DATA HANDLING SYSTEM AND LIGHTING
DISPLAY
Abstract
A data handling system has an arrangement in which input data
may be recorded and/or displayed in analog form while at the same
time the data is encoded in digital form on a storage or memory
medium, such as magnetic tape. When the memory medium is operated
for retrieval of the encoded data, the data is converted to one
analog form for display while at the same time the originally
recorded analog form may also be displayed, whereby two analog
displays result. The system is described as embodied in an
electronic organ and may be used as a teaching device wherein a
series of electric lamps are mounted respectively above a series of
organ keys. A key may be depressed causing the audio to be heard.
At the same time audio is recorded along with data in digital coded
form representing the key. Upon playback the audio is reproduced to
constitute one analog form and the decoding circuitry causes the
lamp associated with the key to be illuminated to provide the
second analog form.
Inventors: |
Wheelwright; Robert W.
(Buffalo, NY) |
Assignee: |
The Wurlitzer Company (Chicago,
IL)
|
Family
ID: |
22620052 |
Appl.
No.: |
05/170,489 |
Filed: |
August 10, 1971 |
Current U.S.
Class: |
84/464R; 84/470R;
84/478; 84/DIG.29; 84/647; 984/302 |
Current CPC
Class: |
A63J
17/00 (20130101); G10H 1/005 (20130101); G10H
1/0016 (20130101); G10H 2220/026 (20130101); Y10S
84/29 (20130101) |
Current International
Class: |
A63J
17/00 (20060101); G10H 1/00 (20060101); A63j
017/00 () |
Field of
Search: |
;84/1.01,1.18,464 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
29,615 |
|
Dec 1912 |
|
GB |
|
719,560 |
|
Dec 1954 |
|
GB |
|
Primary Examiner: Wilkinson; Richard B.
Assistant Examiner: Witkowski; Stanley J.
Claims
The invention is claimed as follows:
1. In a musical instrument having a keyboard, the keys of which are
operable to produce selected audio tones, a series of electric
lamps adjacent to the keyboard, each lamp corresponding to a key,
first means operable responsive to actuation of a selected key for
encoding data in digital form representing the selected key, a
storage medium for said data, second means for processing the data
from the first means and delivering the processed data to said
storage medium, third means for retrieving said data from said
storage medium, and fourth means for processing said retrieved data
and delivering a signal to the lamp associated with the selected
key.
2. In an instrument according to claim 1, means for recording the
audio tone for the selected key upon actuation thereof, and means
for reproducing the audio tone upon retrieval of said data and
actuation of said lamp by the signal delivered thereto.
3. In an instrument according to claim 1, said first means
including a binary coding matrix for coding the key-indicating data
in para lel bit form, and second means including a
parallel-to-serial converter for converting said data to serial
form, whereby the data is stored on said storage medium in serial
form.
4. In an instrument according to claim 3 further including pulse
generating means forming part of said first means and operable
responsive to actuation of said selected key for enabling the
loading of data into said parallel-to-serial converter.
5. In an instrument according to claim 4 further including means
forming part of said first means and providing a signal derived
from the audio tone for clocking the operation of said
parallel-to-serial converter.
6. In an instrument according to claim 5 further including means
for adding data bits of predetermined logic states in said
converter to the data represented by the selected key whereby the
data sent to said storage medium includes said added data bits.
7. In an instrument according to claim 1, fifth means forming part
of said second means for adding additional bits to the data
representing the key, and sixth means forming part of said third
means for utilizing said additional bits as a control for the flow
of the remaining bits to said fourth means.
8. In an instrument according to claim 7 further comprising a
latching network also forming part of said fourth means and
controlled by said sixth means such that the loading of said
remaining bits in said latching network is ascertained by the
presence of said additional bits in said sixth means.
9. In an instrument according to claim 7 further comprising a
decimal coder also forming part of said fourth means for combining
some of the data bits sent from said latching network, and BCD to
decimal converter means also comprising part of said fourth means
that receive data bits in parallel form from said latching network
and said decimal coder for driving said lamp.
10. In an instrument according to claim 5 in which said storage
means comprises a multi-channel magnetic tape in which the data is
stored on one channel, and said audio tone is stored on the other
channel.
11. In an instrument according to claim 4 including means for
clocking said parallel-to-serial converter independently of said
audio tone, the data and clock signal being recorded on a single
channel of the storage medium.
12. In an instrument according to claim 11, said third means
including means for detecting said clock signal from the data
output from said storage medium.
Description
This invention relates to a data handling system, more particularly
to a system that utilizes digital control for the data.
It is an object of this invention to provide a system in which
input data may be recorded and/or displayed in analog form while at
the same time the data is encoded in digital form on a storage or
memory medium. When the memory medium is operated for retrieval of
the encoded data, the data may, by suitable circuitry, be converted
from digital to analog form for display. At the same time the
originally recorded analog form may also be displayed. Thus, the
playback or retrieval may be in two analog forms for simultaneous
reproduction. The preferred storage medium is a tape cassette.
It is a further object of the present invention to provide a system
of the type stated which may be embodied in an audio-visual
instruction arrangement for musical instruments, such as electronic
organs.
In accordance with one form of the invention a light panel is
mounted above a conventional organ keyboard. The panel may, by way
of example, contain 25 lamps such that each lamp corresponds to one
of 25 consecutive keys. A 25 note coding arrangement, corresponding
to the respective keys, is used to record in digital coded form the
output of a key while at the same time the audio tone for the key
is simultaneously recorded. The coded data for the key and the
audio tone are preferably recorded on a tape cassette that is used
with a tape player/recorder built into the organ. One channel of
the recorder is used to record the audio tone while the other
channel is used to record the data that identifies the key. Both
channels are used to effect decoding during playback since the
channel containing the audio tone is utilized as a clock signal
control. Also, when the tape cassette is played back, the audio
tone is reproduced in the audio reproduction system of the organ.
At the same time the lamp above the key corresponding to the audio
tone is illuminated, the operation of the lamp being determined by
the output of the decoding circuitry. This arrangement provides an
effective audio and visual teaching device. Furthermore, since the
signal from which the clock frequency is derived and the data
identifying the key are recorded on separate channels of the tape,
the playback speed of the cassette is not critical.
In another form of the invention for use in audio-visual organ
instruction, a single channel tape cassette may be used. In such an
arrangement, the digital code, in binary form, and its associated
clock-control signals, are converted to certain audio tones
corresponding to binary states 1 and 0. These frequencies are then
modulated by a fixed clock frequency so that the composite signal
is self-clocking. Thus, in a two channel cassette, one channel
would be used for recording the data while the other channel would
have unrestricted informational use.
Further objects of the present invention will be apparent from the
following description taken in conjunction with the accompanying
drawings forming a part thereof.
In the drawings:
FIG. 1 is a perspective view of an organ embodying the present
invention;
FIG. 2 is a block diagram of the coding system of the present
invention;
FIG. 3 is a block diagram of the decoding system of the present
invention;
FIG. 4 is a schematic of the coding matrix which forms part of the
present invention;
FIG. 5 is a truth table for the coding matrix of FIG. 4;
FIG. 6 is a schematic of the coding system of the present
invention;
FIGS. 7 and 8 are schematics of the data and clock interface
portions, respectively, of the decoding system;
FIGS. 9A and 9B taken together constitute a schematic of the logic
portion of the decoding system;
FIG. 10 is a coding block diagram of a modified form of the present
invention; and
FIG. 11 is a decoding block diagram for use with the coding
arrangement of FIG. 10.
Referring now in more detail to the drawing, and particularly to
FIG. 1 thereof, there is shown an organ console 100 having
keyboards 102, 104 and a tape recorder and playback unit 106 of a
cassette type built into the organ at one end of the keyboard 102.
Above the upper keyboard 104 is a panel containing 25 lamps,
collectively identified as L in FIG. 1. Each lamp corresponds to
one of 25 consecutive keys of the keyboard 104. As will be seen
later with reference to FIGS. 9A and 9B, these lamps may be
illuminated in accordance with the decoding circuitry described
herein. In FIG. 4 the keys are shown numbered 1 through 25, and in
FIG. 2 several of the keys are shown with their associated numbers,
the remaining numbers being omitted so as not to obscure the
figure. As will be seen hereafter, when a particular key is
depressed, the audio tone for that key is recorded on one track of
the recorder 106 and coded data representing that key will be
recorded on another track of the recorder. The audio tone is also
used to derive a clock signal in the coding. When the recorder is
operated in the playback mode, the audio tone for that key will be
reproduced in the sound system of the organ, and at the same time
the lamp corresponding to that key, namely the lamp immediately
above the key, will be illuminated. The keys may be depressed in
any succession to produce a series of audio tones and a
corresponding series of lamp illuminations. This will provide both
an audio and a visual teaching device.
Referring now to FIGS. 4 and 5, it will be seen that each key 1
through 25 is adapted to close its associated switch 1s through
25s, the switches forming part of a binary coding matrix 108. As
shown, the binary coding matrix 108 is powered from a suitable
power supply at 110 through resistors 112 and to a number of diodes
114 that are interconnected with each other and with terminals of
the respective switches 1s, 2s, 3s, etc., as is clearly shown in
FIG. 4. The output lines of the decoding matrix are identified as
A, B, C, D and E, thereby to provide a five bit binary coded output
from the coding matrix 108 each time one of the keys is depressed.
The truth table of FIG. 5 shows the binary states of the outputs A,
B, C, D, E for each key. These outputs A, B, C, D, E are also shown
in FIGS. 2 and 6 and constitute input lines for transmitting data
to a parallel-to-serial converter 116, which is a synchronous,
parallel-load, eight-bit shift register.
Each of the keys 1 through 25 is also operatively connected to a
switch 118 shown in FIG. 6. Switch 118 forms a part of a pulse
keyer 120, the circuit for which is shown in FIG. 6 and consists of
diodes 115, 115, capacitor 117, resistors 119, 121 and
resistance-coupled transistors 123, 123. Closing switch 118 causes
a pulse to issue on conductor 122. This pulse keyer circuit 120
provides a control pulse for loading the binary code from the
outputs A, B, C, D, E into the parallel-to-serial converter 116.
Thus, the output from the pulse keyer 120 over conductor 122 is to
the shift/load or gate input (terminal no. 15) of the converter
116.
The converter 116 is packaged as a standard type 74166 integrated
circuit. A circuit of this type is commercially available and is,
therefore, not described in detail. Furthermore, the standard type
74166 and the other integrated circuits hereinafter described are
also identified by circuit numbers since such units are known in
the art and are commercially available, for example from Texas
Instruments, Inc., Dallas, Tex. The various numbered terminals
appearing on the integrated circuits shown herein correspond to the
standard terminal numberings on those units, the function of each
of which is known and understood by those in the art.
Further with reference to FIG. 6, the data input lines A, B, C, D,
E are connected to terminals numbered 4, 5, 12, 11, 10 of the
converter 116, which are the parallel input terminals for the
converter. Three additional data bits, which are used for control
and error detection purposes in the decoding system, are added in
the converter to the five binary bits ABCDE received from the
coding matrix. These three additional data bits are added as states
1, 0, and 1 to input terminals numbered 2, 3 and 14 of converter
116.
The parallel data are loaded into the converter 116 upon receipt of
a keying pulse over conductor 122. When clocked (as hereafter
described) the serial data from the converter 116 will issue over
conductor 124 that is connected to the serial output (terminal no.
13) of converter 116. The converter 116 operates to provide a
serial output 10ABCDE1 on conductor 124, as shown in FIG. 2. The
audio tone from the organ is transmitted over conductor 126 to
channel no. 1 of the tape recorder and also to the inverting input
(terminal no. 4) of an operational amplifier 128 through input
resistance 130. This amplifier 128 is also an integrated circuit,
type 1709 having operating characteristics which are a function of
the external feedback components. Resistors 132, 134 and r.f.
bypass capacitors 136, 138 are connected to the terminals
indicated, resistor 134 being a feedback resistor. The amplifier
128 and circuit 140 constitute a clock converter 142 (FIG. 2). This
clock converter processes the normal audio tone of the organ and
converts it to a suitable clock signal for the converter 116 to
regulate the width of its output pulses, which constitute the data
bits. The output from the amplifier 128 through resistor 144 is
connected to the input terminal of the circuit 140, which in the
present example of the invention may be a type 7413 integrated
circuit. This circuit 140 includes two NAND gates each with four
inputs and an output. The output from the circuit 140 is sent over
conductor 146 to the clock input terminal (no. 7) of the converter
116. The circuit to terminal no. 6 serves as a test point for the
clock.
When a clock signal is sent over conductor 146, the data in the
converter 116 will be sent out over conductor 124 in serial form,
as aforesaid. To insure full data loading of the converter 116, the
amplifier 128 is constructed so that the signal output from the
circuit 140 will be delayed enough to complete the loading of the
converter 116.
To preclude the likelihood recording of degraded data signals in
the tape recorder cassette, the data signals are desirably sent to
buffer/differentiator 148 which may take the form of a type 75450
integrated circuit with an output circuit consisting of resistors
152, 154 and capacitor 156. The differentiated output signal is
sent over conductor 158 to channel no. 2 of the tape recorder 106.
As seen in FIG. 2 the approximate shape of the wave form of the
differentiated signal is shown adjacent to conductor 158. The wave
forms associated with other conductors shown in the drawing herein
are also illustrated.
As thus far described, the tape recorder 106 is turned on and set
in the recording mode prior to depressing a selected organ key.
When the selected key is depressed, the audio tone is recorded on
channel no. 1 of the recorder and this audio tone is used for
deriving the clock signal to converter 116. Switch 118 is also
closed by the organ key which loads data from the coding matrix 108
into the converter under control of the signal from the pulse keyer
120. Data in serial form is sent from converter 116 through
buffer/differentiator 148 and is recorded on tape channel no. 2 in
serial form.
For playback, the recorder 106 is set in playback mode so that the
stored signals may be sent to suitable decoding circuitry as shown
in FIGS. 3, 7, 8, 9A and 9B to illuminate the lamp corresponding to
the selected key.
Referring to FIGS. 3 and 8, the audio tone from channel no. 1 is
sent over conductor 160 to the audio reproduction system of the
organ. The audio signal is also sent to amplifier arrangement 162
comprising two general type 709 operational amplifiers 164, 166,
namely, integrated circuits 1709L and 72709N, respectively, and a
NAND gate circuit 188, which is a type 7413N integrated circuit.
The inversion inputs and the outputs of the two amplifiers are at
terminals 4 and 10 of each, the non-inverting input being at
terminal no. 5 of each. The external feedback and other components
consisting of resistors 170, 172, 174, 176, 178 and capacitors 182,
184, 186 are connected to the terminals indicated in the drawing.
The second amplifier 166 serves as a Schmitt trigger.
The output at conductor 168 is sent through a transistor circuit
180 for driving the circuit 188 and operates as an additional
Schmitt trigger to produce a square wave clock signal of correct
rise and fall time characteristics on conductor 190 (see FIGS. 3
and 8). Thus, the clock converter of FIG. 3 may be considered as
being made up of a portion of the circuit 166 and circuit 188.
Signals for operating the circuit 188 are from conductors 192, 194
which are across resistor 196 in the transistor circuit 180. The
transistor circuit 180 is a clipping/squaring stage. Conductor 192
maintains a signal on the input terminals numbered 9, 10, 12 and
power supply terminal no. 14. When a signal is applied from
conductor 192, the NAND gate conducts giving a pulse at output
terminal no. 8 on conductor 190. Thus, the clock pulse on 190,
which is derived from the recorded audio tone from cassette, is
sent to a serial-to-parallel converter 198 (FIGS. 3 and 9).
Referring to FIGS. 3 and 7, it is seen that the output data signals
from channel no. 2 of the tape recorder 106 is over conductor 200,
and this signal is sent to the inverting input of amplifier
arrangement 202. The amplifier arrangement 202 includes two general
type 709 operational amplifiers 202a, 202b comprised of integrated
circuits, namely types 1709L and 72709N. The external components
comprising resistors 206, 208, 210, 212, 214 and capacitors 216,
218, 220, 222 are connected in circuit and to the standard numbered
terminals indicated in FIG. 7. Two amplifier circuits are used to
provide adequate amplification and to return the signal to proper
phase relationship. Resistor 208 and capacitor 216 are used for
input lag compensation. Output lag is provided by capacitor
220.
As seen in FIG. 3, the output from the amplifier arrangement 202 is
sent to a peak level detector 226 which drives a Schmitt trigger
228. Peak level detection is desired in order to detect the data
stream and eliminate lower level extraneous signals. The peak level
detector and Schmitt trigger process the data signals to a form in
which they may be loaded via conductor 230 into the
serial-to-parallel converter 198.
The peak level detector 226 and Schmitt trigger circuit 228 are
also shown in FIG. 7. The Schmitt trigger circuit 228 is type 1709
operational amplifier while circuit 234 is a type 7410 integrated
circuit, which is a three input positive NAND gate. Circuit 228 has
its inverting input connected through resistor 236, the remaining
components, namely resistors 238, 240 capacitors 242, 244, 246
being connected to the standard numbered terminals of circuit 228
as shown in FIG. 7. The threshold voltage of the circuit 228 is set
by the feedback resistor 238 and the resistor 240 from terminal no.
5 to ground. The output terminal of circuit 228 is connected
through resistor 248 and conductor 250 to the input of the NAND
gate circuit 234. The NAND gate circuit 234 provides a logic signal
compatible with the input signal requirements of the hereinafter
described shift registers 254, 256 of FIG. 9A. Thus, for block
diagram purposes as in FIG. 3, circuit 232 may be considered as
part of the Schmitt trigger 228. From the foregoing it will be
apparent that there are serial pulses on conductor 230 representing
the data fed back from channel no. 2 of the tape recorder.
Referring now to FIG. 9A, it will be seen that the
serial-to-parallel converter 198 utilizes two four-bit shift
registers 254, 256 which may comprise two 7495A integrated
circuits. However, a single eight bit shift register may be
constructed for use as the converter 198. In any event, the
converter 198 as a whole must be capable of handling eight bits as
this is the number of bits used in the code of the present example
of the invention.
Conductor 230 is connected to the serial input terminal no. 1 of
the register 254 while the conductor 190 is connected to one of the
two clock terminals of each of the registers 254, 256 in accordance
with the desired direction of bit shift. As the data are clocked
into the shift registers 254, 256, the data bits 10AB will appear
on terminals numbered 13, 12, 11, 10 respectively of the register
254 while the data bits CDE1 will appear on terminals numbered 13,
12, 11, 10 respectively of the register 256, all as clearly shown
in FIG. 9A. The data will be in parallel form. To produce the CDE1
outputs from the second register 256 the output from terminal no.
10 of register 254 and containing the B bit is connected to the
serial input terminal no. 1 of the register 256.
It will be seen from FIGS. 9A and 9B that the data bits ABCDE are
sent over conductors 260, 262, 264, 266, 268 to a latching network
270 (see also FIG. 3), which is, by way of example, made up of two
bistable quad latches 272, 274. Each latch circuit 272, 274 may be
a type 7475 integrated circuit. The data bits ABCD are stored in
the latch 272 while the data bit E is stored in the latch 274.
Referring again to FIG. 9A and FIG. 3, it is noted that the control
bits, namely the code bits 1, 0, 1 are sent to a load indicator 276
which, in the present embodiment, comprises a hex inverter made up
of integrated circuit type 7405. This load-indicator circuit 276 is
utilized to determine the position of the information bits in the
shift registers 254, 256. When the shift registers are fully loaded
with the eight bit code, the code bits 0, 1, 0 are sent over
conductors 280, 282, 284 to terminals numbered 1, 3 and 5 of the
circuit 276. The logic states of those signals are inverted in the
circuit 276 to produce logic 0 outputs from terminals numbered 2, 4
and 6 of circuit 276. A logic state 1 output appears on terminal
no. 4 and this is sent to terminal no. 9 to provide a state 0
output from terminal no. 8. Consequently, when the shift registers
254, 256 are fully loaded, there will be a state 0 output on
conductor 286. At other times the conductor 286 is at a high state,
as determined by the voltage drop across resistor 288.
Referring to FIG. 9B, the signal on conductor 286 drives a
transistorized pulse-stretching circuit 290 having input resistor
292 connected to the transistor base and capacitor 294 shunted from
emitter to collector. The output signal from the circuit 290 on
conductor 296 is sent to a NAND gate circuit 298, which may be a
type 7413 integrated circuit. Such circuit contains a NAND gate
arrangement with four inputs; hence three of the inputs, as
indicated at terminals numbered 9, 10 and 12 may be biased to a
state 1. Thus, a signal on conductor 296 produces an output or
clock signal from terminal no. 8 on conductor 300, which signal is
sent to the clock input terminals numbered 4 and 13 of the latches
272, 274, thereby triggering the latches and releasing the data
therefrom. In passing and with further reference to circuit 290 it
should be noted that the inputs to the circuit 298, and hence the
input at terminal no. 13 thereof, is sufficiently above zero
voltage to provide a power supply voltage for the transistor of the
circuit 290.
Still referring to FIGS. 3, 9A and 9B, three BCD to decimal
converters 302, 304, 306 are used to convert the signals to decimal
code for the purpose of illuminating the lamp that corresponds to
the organ key that was depressed, as previously described. Since
the converters 302, 304, 306 are controlled by a four bit parallel
signal, it is necessary to modify the five bit code ABCDE to
provide a compatible driving signal.
When the latches 272, 274 are clocked to release the data therein,
the A, B and C data signals are sent out over conductors 310, 312,
314 (see FIG. 9B and again on FIG. 9A) to inputs of converters 302,
304, 306. However, the D and E outputs from the latches 272, 274
are combined in a decimal coder 316, which may be a quad NAND gate
integrated circuit type 7400. The D output from the latch 272 to
the coder 316 is over conductor 318 while the E output from latch
274 is over conductor 320. D sent from the terminal no. 8 of
circuit 272 while E is sent from terminal no. 1 of circuit 274. The
D, D, E, E outputs are combined in the quad NAND gate coder 316 to
produce output signals on conductors 324, 326, 328, 330. These
signals constitute the fourth signals for the converters 302, 304,
306, plus a signal that is sent back through one of the latches in
the circuit 274 for operating lamp no. 24 (FIG. 9B). Thus, the
combined D and E bits determine which converter 302, 304, 306, or
lamp no. 24 is activated. The states of ABC select the converter
output and thus determine which lamp of the group is activated. For
example, considering the signal on conductor 330, D.sup.. E = 0 if
and only if D = 1 and E = 1. Only then can the converter 302 be
operated to illuminate any one of the lamps nos. 1 to 7 and 25, as
determined by the logic states of ABC. Likewise, converter 304 will
be operated only if D = 1 and E = 1. The groups of lamps will thus
be activated in accordance with the following truth table:
(D.sup.. E) (D.sup.. E) (D.sup.. E) (D.sup.. E) Con- Lamp verter
Group 0 1 1 1 302 Nos. 1 to 7, 25 1 0 1 1 304 Nos. 8 to 15 1 1 0 1
306 Nos. 16 to 23 1 1 1 0 No. 24
As to lamp no. 24, the output (D.E) over conductor 324 is sent
through a latch of the circuit 274 to produce an output signal on
conductor 340 to transistor stage 342 which acts as a switch for
lamp no. 24. It should be noted that with respect to the other
lamps, they may be operated directly from the integrated circuits
302, 304, 306 since these have open collector configurations.
In the form of the invention shown in FIGS. 10 and 11, the digital
code and clock control signals may be recorded on a single tape
channel so that with a two channel tape recorder, the system could
provide one unrestricted information channel. The arrangement of
FIGS. 10 and 11 utilizes a number of the components previously
described, and like reference numerals in FIGS. 10 and 11 indicate
like parts as described with reference to FIGS. 1-9B. In essence,
FIGS. 10 and 11 utilize a modulation-demodulation system that
converts binary "ones" and "zeros" into selected audio tones. By
way of example, the 1 could be represented by a 1,700Hz tone and
the 0 by a 2,200Hz tone. These tones could be amplitude modulated
by a fixed clock frequency whereby the composite envelope would in
effect be self-clocking.
As shown in FIG. 10, a clock signal generator 400 sends its output
over conductor 402 to the parallel-to-serial converter 116, and the
output of the latter on conductor 404 is sent to a
voltage-controlled oscillator 406. Consequently, the output from
the converter 116 contains the serial data gated by the clock
pulses. The output from the voltage-controlled oscillator will
consist of series of tone bursts of two different frequencies in
accordance with the logic states of the signals on conductor 404.
These signals are sent to an analog gate 410 and the clock pulses
from the clock generator 400 are also sent over conductor 412 to
the analog gate 410. In the analog gate 410, the tone bursts of the
two frequencies are, in effect, modulated by the clock pulses. This
produces an envelope containing the clock signal and data tone
signals. It is this envelope that is sent to the storage medium,
such as one channel of the tape cassette recorder.
Referring now to FIG. 11 that shows the decoding arrangement, the
signals from the tape channel are sent to an amplifier 414, the
output from which is sent to an envelope detector 416 and, over
conductor 418, to a tone decoder 420. In the envelope detector, the
clock signal "envelope" is demodulated and is used to drive a
Schmitt trigger 422, the latter being used for proper pulse timing
and shaping of the clock signal for use with the logic in the
serial-to-parallel converter 198. In the tone decoder 420, the
signals of the two frequencies representing the two logic states of
the data are converted and shaped to provide voltages corresponding
to logic state 1 or state 0. This converts the data back into
serial bit form for transmission over conductor 424 to the
converter 198. The remaining decoding functions are as previously
described, as will be apparent from FIG. 11.
If a multi-channel tape recorder or other multi-channel magnetic
storage medium is used with the arrangement of FIGS. 10 and 11, the
audio tone for the particular organ key depressed can be recorded
and played back from a second channel, or such second channel may
be used for other instructional purposes.
The systems herein are monotonic in that only one note at a time
can be played. However, the systems are adaptable for indicating
chords. For example, a 12 bit code could be used in which four bits
are for a chord, five bits for notes and three bits for loading
information.
* * * * *