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BACKGROUND OF THE INVENTION
The present invention relates generally to telephone recording systems, and
more particularly to a telephone recording system wherein telephone
numbers or numerically-encoded messages are stored and successively
visually displayed on command.
Tape recording units have been commonly used to record information
associated with incoming calls, i.e., messages generated by a number of
different callers. An answer actuator, connected to the telephone line at
the called telephone, captures the telephone line in response to receipt
of a ringing signal generated by the caller. The actuator also initiates
operation of the recorder. The recorder first plays a pre-recorded
instructional message and then automatically switches to a "record" mode
to record verbal information from the caller. Such information may include
the telephone number where the caller can be reached, or other verbal
information such as order placing, etc.
The recorded information is played out of the recorder in serial form, that
is, the called party must listen to each message in the order in which the
message was recorded. Although generally satisfactory for many uses, this
type of read-out is extremely slow. In many instances, the only
information contained in the recording is the telephone number where the
caller can be reached, or numerical information routinely processed by a
dispatcher or order taker, such as a part number or quantity. This
information could be determined at a glance. There exists a need to
provide a quick visual read-out of stored number data on command.
In other instances, audio reproduction of incoming messages is inconvenient
or unacceptable. For example, during a conference, a secretary may wish to
notify her supervisor of an incoming call or convey a message to her
supervisor while he or she is in conference. The supervisor cannot
interrupt the conference to answer the telephone, and frequently no
response is even required. Accordingly, there exists a need for a means of
non-verbally relaying messages, via telephone, thus permitting a called
party to view each message on command, without disrupting a conference or
other personnel. The called party can then decide whether or not it is
necessary to respond to the message.
OBJECTS OF THE INVENTION
One object of the present invention is to provide a new and improved system
for recording incoming messages at a called station.
Another object of the present invention is to provide a system for visually
displaying incoming messages.
Another object of the present invention is to provide a new and improved
recording system connected to the telephone lines for recording incoming
messages for visual display.
Still another object of the present invention is to provide a new and
improved telephone recording system, wherein several sets of incoming
messages are stored at a called station, and then successively visually
displayed on command.
Still another object of the present invention is to provide a new and
improved telephone recording system which provides rapid read-out of
stored messages on command.
Yet another object of the present invention is to provide a new and
improved telephone recording system wherein recording verbal information
is unnecessary.
Still another object of the present invention is to provide a new and
improved telephone recording system which is compact, inexpensive, and
easy to operate.
Yet another object of the present invention is to provide a new and
improved telephone data recording system that is contained at a telephone
set, and wherein no central office or utility pole-mounted equipment is
required.
SUMMARY OF THE INVENTION
In accordance with the invention a telephone recording system comprises
signal detector circuitry for converting numerically-encoded messages
generated via the "touch-tone" or "rotary" dial by a caller into digital
signals, and storing the signals in memory circuitry. Sets of the digital
signals constituting individual messages, or "words", e.g., a caller's
ten-digit telephone number, are stored in the memory circuitry, and are
successively transferred to a visual display on command by the called
party.
An answer actuator, when placed in a "ready" mode, causes the telephone to
capture the telephone line, i.e., to take the telephone "off-hook", in
response to a ringing signal generated by the caller. The actuator also
turns on a power supply for powering the system and supplies an enable
signal to a decimal-to-binary converter for receiving incoming message
data.
After the called telephone has captured the telephone line, the caller
generates numerically-encoded message data via the touch-tone or rotary
dial of his telephone set. Pulses generated by the rotary dial are
filtered in a pulse shaper to eliminate noise and steepen the pulse edges,
and are supplied to the enabled decimal-to-binary converter. In a
touch-tone system, a frequency-to-pulse train converter converts the
push-button tones to pulses and supplies the pulses to the
decimal-to-binary converter. A duration of digit detector (one-shot
multivibrator) at the decimal-to-binary converter controls the sampling
time of the converter in response to the incoming pulses.
In a first embodiment, the output of the decimal-to-binary converter is
connected to the input of a scratch-pad memory having N-stages of storage.
Each output of the decimal-to-binary converter, which is the binary
equivalent of a decimal digit generated by the caller, is stored in the
scratch-pad memory. In practice, I make N = 10 so that the scratch-pad
memory is capable of storing a ten-digit telephone number.
An end of message detector (integrator), which is responsive to a delay
time between input pulses greater than a predetermined delay time,
actuates a first N-pulse pulse train generator that causes transfer of the
contents of all N stages of the scratch-pad memory, constituting a single
message, to a larger main memory. The main memory is large enough to store
several messages successively unloaded from the scratch-pad memory. The
output of the main memory is controlled by a read-out control circuit
comprising a second N-pulse pulse train generator. This generator includes
an N-stage shift register that successively addresses each digit of a set
of N-digit display units. In response to operation of a read-out button,
the shift register causes the main memory to successively transfer the
stored digits of a numerically-encoded N-digit message to the display
units thereby visually displaying one message.
In a second embodiment, the output of the digital-to-binary converter is
connected directly to the main memory; there is no scratch-pad memory
required. Each digit of an incoming message is loaded into the main memory
under the control of the end of digit detector. The end of digit detector
also supplies pre-count pulses to the first N-pulse pulse generator to
preset the generator with M counts, where M is the number of digits in the
message, and is less than or equal to N. At the end of the message,
determined by the end of message detector, the generator supplies (N-M)
pulses to the shift input of the main memory, thereby causing an N-digit
message or data block to be stored therein (N-M stages of the memory
contain no information).
In each embodiment, an overload indicator monitors the data loaded into the
main memory as well as the data unloaded therefrom and transferred to the
display units, and inhibits further loading when the main memory has been
overloaded with message data.
The main memory is operated in a first in -- first out basis, and is
preferably formed of shift registers for economy, with the binary coded
sets of message data stored in series. In response to operation of the
read-out button, a multivibrator advances the earliest recorded message to
the outputs of the shift registers and then unloads that message to the
display units. Alternatively, the main memory may be formed of a random
access memory with messages read out in the order in which they were
stored using addressing.
I am aware of U.S. Pat. No. 3,787,626 to Subreta, disclosing a system for
automatically relaying a caller's telephone number to a called party
before the called party answers his telephone. However, Subreta's system
is responsive to pulses generated by the caller prior to the called
party's capturing the telephone line, and these pulses represent only the
caller's telephone number. There is no provision for generating
numerically-encoded messages to the called party after capture of the
telephone line. There is furthermore no provision for storing multiple
messages, and successively visually displaying them on command. Also,
Subreta's system must be located at a central office or on a telephone
pole.
Still other objects and advantages of the present invention will become
readily apparent to those skilled in this art from the following detailed
description, wherein I have shown and described only the preferred
embodiments of the invention, simply by way of illustration of the best
mode contemplated by me of carrying out my invention. As will be realized,
the invention is capable of other and different embodiments, and its
several details are capable of modifications in various obvious respects,
all without departing from the invention. Accordingly, the drawings and
description are to be regarded as illustrative in nature, and not as
restrictive.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a block diagram of one embodiment of the present invention;
FIGS. 2A and 2B are signal diagrams illustrating the operation of duration
of digit detector shown in FIG. 1;
FIGS. 3A-3C are signal diagrams illustrating the operation of the end of
message detector shown in FIG. 1;
FIG. 4 is a detailed diagram of the scratch-pad memory of FIG. 1, showing
the shift register components;
FIG. 5 is a partial block diagram of another embodiment of the invention
wherein no scratch-pad memory is required;
FIG. 6 is a diagram of one embodiment of a push-button tone-to-pulse train
converter for operation in a touch-tone system;
FIGS. 7A-7D are diagrams of signals generated by the elements shown in FIG.
6;
FIG. 8 is a perspective view of a telephone having the present invention
incorporated therein; and
FIG. 9 is a perspective view of a module containing the system of the
present invention attached to the bottom of a telephone.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 5, a telephone recording system 20, in accordance
with the present invention, comprises a conventional telephone answer
actuator 22 which, in response to a ringing signal on the telephone line,
causes the telephone to "capture" the line. The actuator 22 also energizes
a power supply (not shown) operating the digital circuitry constituting
system 20 and enables decimal-to-binary converter 24. Converter 24
converts numerically-encoded data, received at the telephone, into digital
signals that are stored in a main memory 28. In the embodiment of FIG. 1,
each message is temporarily stored in a scratch-pad memory 26 and then
transferred to the main memory 28 as a data set. In the embodiment of FIG.
5, each message is directly transferred to main memory 28 as a data set
under the control of a presettable N-pulse pulse train generator 48a. In
both embodiments, several sets of numerically-encoded data (messages) are
successively stored in the main memory 28. The messages are then
successively transferred to display circuitry 30 in response to operation
of read-out control 32.
Referring now to the embodiment of FIG. 1 in more detail, in ringing signal
on line 34 is detected by a conventional phone answer actuator 22 that has
been readied by being placed in a "record" mode via a record switch 23.
The record switch 23 is preferably mounted on or in proximity to the
telephone set (see FIGS. 8 and 9). Besides converting the telephone set to
an "off-hook" condition to capture the telephone line, phone answer
actuator 22 also connects a power supply (not shown) to the logic
circuitry contained in system 20, but the memory circuitry is continuously
energized so as to retain any message data stored therein. However, if the
memory circuitry is non-volatile, such as core, the memory may also be
de-energized to conserve power.
Phone answer actuator 22 also supplies an enable signal to terminal E of
decimal-to-binary converter 24. The phone answer actuator 22 subsequently
releases the telephone line and de-energizes the logic circuitry in
response to the calling phone's returning on-hook, or after a
predetermined period of time, in a conventional manner.
The numerically-encoded message data which, in the embodiment of FIG. 1, is
generated by the caller via a conventional rotary telephone dial, are in
the form of pulse trains on data line 36. These pulses are supplied to
pulse shaper 38 which eliminates any noise from the pulses and steepens
the leading and trailing edges, and supplies the shaped pulses to count
terminal C of decimal-to-binary converter 24. The output of pulse shaper
38 is also supplied to end of message detector 44 as well as to duration
of digit detector 40.
The numbers of pulses constituting the data pulse trains at the output of
shaper 38 correspond to the numbers dialed by the caller. For example, in
FIG. 2A, the pulses shown represent the number 42 (the first pulse train
contains four pulses and the second pulse train contains two pulses). A
series of digits forming a message, hereinafter termed "set" contains up
to 10 digits, e.g., a 10-digit telephone number. As described in detail
infra, messages are stored in 10-digit sets, and if a message contains
fewer than 10 digits e.g. M digits, (10 - M) storage spaces in the storage
set remain unoccupied, but the message is stored in memory as a complete
10-digit set.
Decimal-to-binary converter 24 samples each train of pulse; (FIG. 2), and
converts the train to a binary-coded signal. For example,
decimal-to-binary converter 24 would, in operation, convert the digits 4
and 2 respectively to 0100 and 0010. Duration of digit detector 40, which
may be a conventional integrator or pulse detector, supplies an activating
signal to terminal S of converter 24 during the presence of an incoming
pulse train (see FIGS. 2A and 2B). During activation of input terminal S,
converter 24 counts the incoming pulses (FIG. 2A), and when the output
signal of duration digit detector 40 is removed (FIG. 2B), converter 24
accumulates the pulse count and generates a corresponding binary-coded
signal. This binary-coded signal is stored in scratch-pad memory 26.
The operation of scratch-pad memory 26 is synchronized to the output of
duration of digit detector 40. Delay circuit 42, connected between
detector 40 and memory 26, delays the trailing edge of the output signal
of detector 40 before supplying the detector signal to the read and shift
input terminals of scratch-pad memory 26. Accordingly, shortly after the
development of the binary-coded digit by converter 24, the binary-coded
digit is stored in the memory 26. Delay 42 is necessary to ensure that the
binary-coded number is fully developed before it is transferred to the
memory 26. Each time a digit is developed, controlled by detector 40, the
binary-coded representation of the digit is stored in scratch-pad memory
26, and previously stored digits are shifted.
The scratch-pad memory 26 is comprised of four shift registers 26(1)-26(4)
connected in parallel to each other, and each shift register contains N
stages (FIG. 4). N = 10 is chosen so that scratch-pad memory 25 is capable
of storing a ten-digit telephone number, as aforementioned, but a larger
or smaller number of stages of storage could be provided. As will be
described in more detail infra, the number of stages of storage in
scratch-pad memory 26 determines the size of the data sets processed in
system 20.
At the end of each incoming message (up to ten digits), determined by an
end of message detector 44, the contents of all ten stages of scratch-pad
memory 26 are transferred to main memory 28. If fewer then ten stages of
scratch-pad memory 26 are used, e.g., a four-digit code is stored, six of
the stages transferred to main memory 28 will contain no information, but
the contents of all 10 stages will be transferred as a single block or set
of data.
Ead of message detector 44 is preferably an integrator circuit for
detecting the absence of a pulse for a predetermined duration of time. The
absence of pulses indicates that no additional digits are intended to be
sent by the caller. Of course, it is necessary that the caller not
hesitate too long between generation of successive digits of a message,
but the predetermined duration is set for at least several seconds to
avoid generation of unintended end-of-message signals. Optionally,
detector 44 may be a filter circuit responsive to the tone generated by an
auxiliary button (# or *), in a conventional touch-tone system, manually
operated by the caller for indicating end of message.
Referring to FIG. 3A, a message containing three digits, i.e., four, three,
and two, is represented by three pulse trains containing respectively
four, three, and two pulses. These pulses are integrated to form the
waveform shown in FIG. 3B. It is noted that although the magnitude of the
waveform in FIG. 3B decreases somewhat between adjacent pulse trains, the
magnitude does not approach zero until after the occurrence of the
two-digit pulse train (which is at the end of the message). In response
thereto, detector 44 generates a pulse, shown in FIG. 3C, to R-S flip-flop
46 of N-pulse pulse train generator 48.
N-pulse pulse train generator 48 (FIG. 1), where N equals 10 in the
preferred embodiments, generates N shift pulses to scratch-pad memory 26
in response to a pulse generated by detector 44, and serves to transfer
the contents of the N-stage scratch-pad memory 26 to main memory 28. Pulse
generator 48 includes an astable multivibrator 50, controlled by flip-flop
46. A divide-by-N divider circuit is connected between the output of
astable multivibrator 50 and the reset terminal R of flip-flop 46. In
operation, the pulse generated by end of message detector 44 sets
flip-flop 46 which in turn enables astable multivibrator 50. Multivibrator
50 provides a pulse train at output line 52, and divide-by-N divider
circuit 54 feeds the Nth pulse back to reset terminal R of flip-flop 46,
thereby resetting the flip-flop and disabling multivibrator 50. The pulse
train output of generator 48 is supplied to one input of OR gate 56 in
turn connected to shift input SH of scratch-pad memory 26.
The output of pulse train generator 48 is also connected to the shift input
SH of main memory 28, via AND gate 59, and OR gate 58. This arrangement,
as discussed in more detail infra, causes each digit, unloaded from
scratch-pad memory 26, to be individually loaded into main memory 28. The
other input of AND gate 59 is connected to the output of overload circuit
33. As also discussed infra, this connection prevents any overloading of
main memory 28.
At the end of message, determined by end of message detector 44, pulse
generator 48 generates an N-pulse pulse train to transfer the contents of
the N-stages of scratch-pad memory 26 to main memory 28. No new data are
read into scratch-pad memory 26 until new message digits are received by
the system 20 and new shift pulses are generated by duration of digit
detector 40. As aforementioned, main memory 28 has a storage capacity
large enough to accommodate several sets of N-digit messages loaded from
scratch-pad memory 26 and, in practice, I provide at least 100 stages of
storage in the main memory to accommodate ten sets of ten-digit messages.
Each set of message digits is unloaded from main memory 28 on command by
closing read-out switch 32. Read-out switch 32 controls the operation of a
second N-pulse pulse train generator 60 (where N = 10) comprising an R-S
flip-flop 62, an astable multivibrator 64 and an N-stage shift register
66.
Closure of read-out switch 32 causes a logic 0 to be applied to the set
terminal S of flip-flop 62 thereby causing the output of the flip-flop to
go to logic 1. The logic 1 output of flip-flop 62 turns on astable
multivibrator 64, and the pulses generated by the astable multivibrator
are supplied through one input of AND gate 67, to the input I and shift
terminal SH of shift register 66. Pulses, generated by astable
multivibrator 64 are also supplied to shift input SH of main memory 28
through OR gate 58. Pulses, generated by the multivibrator 64 are,
however, not loaded into shift register 66 for causing display of output
of memory 28 until the earliest message digit, stored in the memory, has
been shifted down to the memory output. This prevents any "data gaps" from
occurring during read-out requiring the user to successively operate
read-out button 32 until a message appears on display 30. Shift register
66 does not enable read-out of memory 28 until a message digit has been
shifted down to the memory output because the pulses generated by
generator 60 are not loaded into the shift register 66 until a logic 1
appears at any of the output terminals of main memory 28, monitored by OR
gate 71. The output of OR gate 71 is connected to AND gate 67 in pulse
generator 60. Thus, in response to a closure of read-out switch 32,
multivibrator 64 generates pulses that shift data stored in main memory 28
until a first message digit (containing at least one logic 1 bit) is
detected at the output of the memory by OR gate 71 (obviously, this
requires that the first binary-encoded message digit not contain all
zeros). Then, the pulses generated by multivibrator 64 are also loaded
into input I of register 66 via AND gate 67, and shift register outputs 1,
2 . . . N successively go to logic 1. When the Nth output of shift
register 66 is at logic 1, this logic 1 signal is fed back to the reset
terminal R of flip-flop 62, via OR gate 68 to reset flip-flop 62 and
turn-off astable multivibrator 64. At that time, the outputs 1, 2 . . . N
of shift register 66 are all at logic 1, and remain in that state until
the shift register is reset by a logic 0 signal applied to the reset
terminal R of the shift register. This occurs when system 20 is reset
manually via a reset switch RESET (FIG. 1), or by a reset pulse RP
generated by read-out switch 32. The N pulses generated by multivibrator
64 during loading of stages 1, 2 . . . N of register 66 are also supplied
to the shift input SH of main memory 28. The result is that the earliest
N-digit data set stored in memory 28 and serially "lined up" at the
output, is unloaded therefrom.
The outputs of main memory 28 are connected to the data inputs of latching
switches 70(1), 70(2) . . . 70(N). The outputs of switches 70(1), 70(2) .
. . 70(N) are connected respectively to display units 72(1), 72(2) . . .
72(N). Display units 72 are any suitable alpha-numeric display unit such
as nixie tubes, liquid crystal, or light-emitting diode displays. The
displays 72 also contain conventional binary-to-decimal conversion
circuitry for decoding the four-bit binary-encoded data input to decimal
data for operating the display.
Latching switches 70(1), 70(2) . . . 70(N) are controlled by the outputs of
shift register 66. The output terminals 1, 2 . . . N of register 66 are
connected respectively to the control inputs of switches 70(1), 70(2) . .
. 70(N), and as the shift register is loaded with logic 1 pulses, the
switches successively turn on, thereby energizing the respective display
units. Each latching switch 70 is conventional, and after latched on to
store a digit, blocks out any additional digits, supplied to its input,
until reset.
The first pulse generated by astable multivibrator 64 that is loaded into
shift register 66 causes output 1 of the shift register to go to logic 1.
Since output 1 of shift register 66 is connected to the control input of
switch 70(1), that switch latches on, and the digit unloaded from main
memory 28 is transferred to display 72(1), via switch 70(1). The second
pulse generated by astable multivibrator 64 unloads another digit from
main memory 28, and this digit is supplied to display 72(2) via switch
70(2) latched on by the signal at terminal (2) of shift register 66. At
this time, there are logic 1 outputs at both terminals (1) and (2) of
shift register 66, and the first and second digits are stored respectively
in latching switches 70(1) and 70(2). The unloading of main memory 28
continues until all digits of a message are loaded into the latching
switches 70(1) 70(2) . . . 70(N). These switches 70 remain latched and
store the respective digits, successively unloaded from main memory 28, so
that the message remains visible on display units 72(1), 72(2) . . .
72(N).
The latching switches 70(1), 70(2) . . . 70(N) are subsequently reset by
supplying a logic 0 signal to the reset terminals R of the switches. This
is effected automatically each time read-out switch 32 is depressed just
prior to generation of pulses by astable multivibrator 64. Logic racing is
avoided since there is inherent delay associated with flip-flop 62 and
astable multivibrator 64, so that switches 70(1), 70(2) . . . 70(N) are
reset prior to loading of new data controlled by output terminals 1, 2 . .
. N of shift register 66. Differentiator 74, connected between the output
of read-out switch 32 and the latching switches 70(1), 70(2) . . . 70(N)
causes only a single reset pulse to be generated even if read-out switch
32 is maintained closed by the user, and this prevents accidental reset
during unloading of main memory 28.
Summarizing the loading and unloading of digits with respect to main memory
28, at the end of each incoming message, a pulse generated by detector 44
causes an N-digit data set containing an M-digit message to be transferred
from scratch-pad memory 28 to main memory 28. Main memory 28 is capable of
storing P data sets, and in practice, I make N equal to ten and P at least
about ten. When a message is to be read out, operation of read-out button
32 initiates oscillation of multivibrator 64 to shift the earliest stored
message in memory 28 down to the memory output. Then, under control of
N-stage shift register 66, the earliest stored data set is unloaded from
memory 28 to display 30.
Obviously, it is necessary that additional messages be inhibited from being
transferred from scratch-pad memory 26 into the main memory 28 when the
main memory is loaded to capacity. Overload monitor 33 (FIG. 1) inhibits
the shift input of main memory 28, and supplies an overload indication
whenever the main memory is filled to capacity (contains ten messages).
Monitor 33 comprises an up/down counter 35 which is up-counted by the
output of N-pulse pulse train generator 48 (loading main memory 28) and
down-counted by the output of N-pulse pulse train generator 60 (unloading
main memory 28). The output of up/down counter 35 is compared to a preset
number (indicating memory capacity) in comparator 37. An output from the
comparator is supplied as an alarm to the user, and also fed back to AND
gate 59 to inhibit additional loading of main memory 28. Any additional
loading of memory 28 would cause loss of message data by passing the
earliest stored messages out of the memory via output terminals O.sub.1
-O.sub.4 thereof.
Referring now to FIG. 5, a second embodiment of system 20 is described,
wherein scratch-pad memory 26 is not required. In FIG. 5, each M-digit
message is transferred directly from counter 24 to main memory 28 as an
N-digit data set (N-M digits of the data set are encoded as all-zeros and
carry no information). At the end of each message digit incoming on line
36, a pulse generated by duration of digit detector 40, is supplied (1) to
terminal S of counter 24 in order to convert the incoming digit to a
binary-encoded digit, and (2) to shift terminal SH of main memory 28, via
delay 42 and gates 57, 58 and 59, to store the binary-encoded digit in the
memory. The output of delay is also connected to one input of OR gate 61
in generator 48. The other input of OR gate 61 is connected to the output
of multivibrator 50. The function of OR gate 61 is to store counts in
divider 54 in response to pulses generated either by multivibrator 50 or
by duration of digit detector 40. Thus, assuming an M-digit message is
received on line 36, divider 54 becomes preset to the count M, and the M
digits are stored in memory 28 in response to M pulses generated by
duration of digit detector 40. At the end of the message, in response to a
pulse generated by end of message detector 44, multivibrator 50 is
enabled. However, multivibrator 50 generates only (N-M) pulses before it
is reset by divider 54 and flip-flop 46, because the (N-M)th pulses,
generated by the multivibrator is fed back through the divider. The (N-M)
pulses, generated by multivibrator 50, shift the M-digit message, stored
in main memory 28, another (N-M) stages so as to be stored as an N-digit
data set. This is the same result provided by scratch-pad memory 26 in
FIG. 1.
The discussion of system 20 has been directed toward a rotary dial
telephone system, i.e., wherein message data are generated using the
rotary dial of the telephone. The rotary dial generates pulse trains
having numbers of pulses corresponding to the number dialed. However, in a
touch-tone system, the pulse shaper 38 is replaced by a touch-tone
converter circuit. The touch-tone converter circuit converts the audio
tones, generated in response to operation of each of the buttons of a
touch-tone dial, to a pulse train having a number of pulses corresponding
to the particular button operated. Such converters are well-known in the
prior art, and are referred to in Electronics, Dec. 11, 1975, at page 100.
One example of such a converter circuit is shown in FIG. 6.
Referring to FIG. 6, touch-tone converter 82 comprises a filter 84 for
filtering extraneous noise from a two-frequency touch-tone audio signal,
and converting the two-frequency touch-tone audio signal to a
single-frequency signal representation of the touch-tone button operated.
This may, for example, be effected using a memory which is hardwire
programmed to generate a pulse train having a length corresponding to the
address created by the incoming touch-tone signals. The output of filter
84 is shown in FIG. 7A, which represents two successive touch-tone signals
wherein the second signal has a higher frequency. Obviously, the waveform
in FIG. 7A is much shorter than the waveforms generated in practice, but
is exemplary of the frequency relationships. The output of filter 84 is
supplied to sine-to-pulse converter 86 which converts the sinusoid to
pulses, as shown in FIG. 7B. The pulse density of second pulse train is
larger than the first in correspondence with the sinusoids in FIG. 7A. The
output of the sine-to-pulse converter 86 is sampled with a switch 88
controlled by a fixed frequency astable multivibrator 90. The output of
multivibrator 90 is shown in FIG. 7C, and causes switch 88 to transfer
pulses generated by converter 86 within constant time intervals. The
output of switch 88 shown in FIG. 7D, is thus proportional to the
frequency of the signal at the output of converter 86, and corresponds to
the data signal at the input of filter 84. For example, pulse frequency
converter 92 generates a pulse train having three pulses in response to an
incoming touch-tone signal generated by the touch-tone button "3" on the
telephone set.
System 20 can be incorporated directly within an office telephone set, as
shown in FIG. 8, with unused buttons functioning as the record button and
read button operating respectively phone answer actuator 22 and read-out
switch 32 in FIG. 1. Display units 72 are exposed through a rectangular
aperture formed in the casing of the telephone. Optionally, system 20 can
be provided as a separate module 92 (FIG. 9) mounted in proximity to the
telephone set or attached to the bottom thereof, as shown. The read button
and record button, as well as the display 72, are provided on the exterior
of the module.
In summary, a message recording system for a telephone, for visually
displaying message data transmitted via the touch-tone or rotary dial of a
telephone set has been described. The system is comprised of solid state
circuitry that captures the telephone line in response to a ringing
signal, and then stores numerically-encoded messages transmitted by the
caller via his dial. The messages are then successively displayed on an
alpha-numeric display panel, on command. The circuitry is preferably
comprised of integrated circuit modules, such as CMOS, but other logic
families could be used, as well as discrete components. The entire system
is light and compact, and consumes very little power. Where a modular unit
is used, as in FIG. 9, the system 20 can be adapted for use with any of
the various telephones in an office, and the converter circuit 82 (FIG. 5)
permits use with touch-tone, as well as rotary dial, telephone sets. Also,
the system 20 can be hard-wire coupled to the telephone line, or could be
magnetically or sonically coupled thereto. Of particular importance,
system 20 is connected up at the telephone set itself, rather than at a
central office or telephone pole.
In this disclosure, there is shown and described only the preferred
embodiments of the invention, but, as aforementioned, it is to be
understood that the invention is capable of use in various other
combinations and environments and is capable of changes or modifications
within the scope of the inventive concept as expressed herein. For
example, although a 10-digit data set has been described, obviously, other
numbers of digits could be used. For example, in a four-digit system,
which would be suitable for relaying most numerically-encoded messages,
and telephone extension numbers, scratch-pad memory 26 would comprise a
set of four-stage shift registers, and main memory 28 would comprise a set
of 40-stage shift registers, large enough to store 10 sets of messages.
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