Communication system incorporating signal delay

Claim 2

A communication receiver for receiving incoming signals including a sequence of a reference tone and at least one control tone, said receiver comprising a processing circuit for receiving the incoming signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the one control tone in the other sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one low-frequency mixed signal having a frEquency representative of the difference between the frequencies of the reference tone and the one control tone, and utilization means coupled to said mixing means for using the mixed signal.

Claim 3

The communication receiver set forth in claim 1, for receiving a sequence of a reference tone and a single control tone, said mixing means providing a single low-frequency mixed signal with a frequency equal to the difference between the frequencies of the reference tone and the single control tone.

Claim 4

The communication receiver set forth in claim 1, for receiving a sequence of a reference tone and a plurality of control tones, said mixing means providing a sequence of low-frequency mixed signals corresponding in number to the number of control tones, the frequencies of the low-frequency mixed signals being respectively equal to the frequencies of the control tones minus the frequency of the reference tone.

Claim 5

The communication receiver as set forth in claim 1, wherein said delay means includes a shift register and a clock coupled thereto.

Claim 6

The communication receiver set forth in claim 1, wherein said mixing means includes an Exclusive-Or circuit having two inputs respectively coupled to said processing circuit and to said delay means and an output coupled to said utilization means.

Claim 7

The communication receiver set forth in claim 1, wherein said utilization means includes decoding means responsive to a mixed signal having a predetermined frequency to provide an output signal.

Claim 8

The communication receiver set forth in claim 6, wherein said decoding means includes an electronic switch to cause the output signal to be DC.

Claim 9

The communication receiver set forth in claim 1, and further comprising limiter circuit means having an input coupled to said processing circuit and an output coupled to said delay means and to said mixing means, said limiter circuit means being operative to render substantially constant the amplitude of the processed signals applied to said delay means and to said mixing means.

Claim 10

A communication receiver for receiving incoming signals including a sequence of a reference tone and at least one control tone, said receiver comprising a processing circuit for receiving the incoming signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the one control tone in the other sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one low-frequency mixed signal having a frequency representative of the difference between the frequencies of the reference tone and the one control tone, band-pass filter means tuned to pass the reference tone and not the control tone and connected in the path followed by that sequence in which the reference tone is at least partially in time coincidence with the control tone in the other sequence, and utilization means coupled to said mixing means for using the mixed signal.

Claim 11

A communication receiver for receiving incoming signals including a sequence of a reference tone and at least one control tone, said receiver comprising a processing circuit for receiving the incoming signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the one control tone in the other sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one low-frequency mixed signal having a frequency representative of the difference between the frequencies of the reference tone and the one control tone, band-pass filter means tuned to pass the reference tone and not the control tone and connected in the path followed by that sequence in which the reference tone is at least partially in time coincidence with the control tone in the other sequence, and utilization means coupled to said mixing means for using the mixed signal.

Claim 12

The communication receiver set forth in claim 9, wherein said band-pass filter means is coupled in the path containing said delay means.

Claim 13

The communication receiver set forth in claim 9, wherein said band-pass filter means is coupled to the output of said delay means.

Claim 14

A communication receiver for receiving incoming signals including a sequence of a reference tone and at least one control tone, said receiver comprising a processing circuit for receiving the incoming signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the one control tone in the other seqUence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one high-frequency mixed signal and at least one low-frequency mixed signal, the high-frequency mixed signal having a frequency greater than the frequencies of the reference tone or the one control tone, the low-frequency mixed signal having a frequency equal to the difference between the frequencies of the reference tone and the one control tone, low-pass filter means coupled to said mixing means and having a cutoff frequency between the frequencies of the high- and low-frequency mixed signals so as to pass only the low-frequency mixed signal, and utilization means coupled to said low-pass filter means for using the low-frequency mixed signal.

Claim 15

A communication receiver for receiving incoming signals including a sequence of a reference tone and at least one control tone, said receiver comprising a processing circuit for receiving the incoming signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the one control tone in the other seqUence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one high-frequency mixed signal and at least one low-frequency mixed signal, the high-frequency mixed signal having a frequency greater than the frequencies of the reference tone or the one control tone, the low-frequency mixed signal having a frequency equal to the difference between the frequencies of the reference tone and the one control tone, low-pass filter means coupled to said mixing means and having a cutoff frequency between the frequencies of the high- and low-frequency mixed signals so as to pass only the low-frequency mixed signal, and utilization means coupled to said low-pass filter means for using the low-frequency mixed signal.

Claim 16

The communication receiver set forth in claim 12, wherein said low-pass filter means includes amplifier means for amplifying the low-frequency mixed signal.

Claim 17

A communication receiver for receiving incoming signals including a sequence of a reference tone and at least one control tone followed by an intelligence message, said receiver comprising a processing circuit for receiving the incoming signals and providing an undelayed sequence of tones and the intelligence message, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the one control tone in the other sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one low-frequency mixed signal with a frequency representative of the difference between the frequencies of the reference tone and one control tone, decoding means responsive to a mixed signal having a predetermined frequency to provide an output signal, electronic switching means coupled to said decoding means and responsive to the output signal of providing an enabling signal which extends beyond termination of the delayed sequence, and an output circuit coupled to said processing circuit and including a transducer for converting the intelligence message, said output circuit being coupled to said electronic switching means and responsive to the enabling signal to furnish an output in accordance with the intelligence message and rendered inoperative in the absence of the enabling signal.

Claim 18

A communication receiver for receiving incoming signals including a sequence of a reference tone and at least one control tone followed by an intelligence message, said receiver comprising a processing circuit for receiving the incoming signals and providing an undelayed sequence of tones and the intelligence message, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the one control tone in the other sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one low-frequency mixed signal with a frequency representative of the difference between the frequencies of the reference tone and one control tone, decoding means responsive to a mixed signal having a predetermined frequency to provide an output signal, electronic switching means coupled to said decoding means and responsive to the output signal of providing an enabling signal which extends beyond termination of the delayed sequence, and an output circuit coupled to said processing circuit and including a transducer for converting the intelligence message, said output circuit being coupled to said electronic switching means and responsive to the enabling signal to furnish an output in accordance with the intelligence message and rendered inoperative in the absence of the enabling signal.

Claim 19

A communication system comprising a transmitter including means for generating a sequence of a reference tone and at least one control tone, and means for transmitting the sequence of tones; and a receiver including a processing circuit for receiving the transmitted signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the control tone in the other sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one low-frequency mixed signal with a frequency representative of the difference between the frequencies of the reference tone and the control tone, and utilization means coupled to said mixing means for using at least the mixed signal.

Claim 20

A communication system comprising a transmitter including means for generating a sequence of a reference tone and at least one control tone, and means for transmitting the sequence of tones; and a receiver including a processing circuit for receiving the transmitted signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being such as to cause the reference tone in one sequence to be in time coincidence with at least a portion of the control tone in the other sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides at least one low-frequency mixed signal with a frequency representative of the difference between the frequencies of the reference tone and the control tone, and utilization means coupled to said mixing means for using at least the mixed signal.

Claim 21

The communication system set forth in claim 15, wherein said generating means generates a sequence of a reference tone and a single control tone, said mixing means providing a single low-frequency mixed signal with a frequency equal to the difference between the frequencies of the reference tone and the single control tone.

Claim 22

The communication system set forth in claim 15, wherein said generAting means generates a sequence of a reference tone and a plurality of control tones, said mixing means providing a sequence of low-frequency mixed signals corresponding in number to the number of control tones, the frequencies of the low-frequency mixed signals being respectively equal to the frequencies of the control tones minus the frequency of the reference tone.

Claim 23

The communication system set forth in claim 17, wherein said reference tone precedes all of said control tones.

Claim 24

The communication system set forth in claim 17, wherein said sequence includes an even number of control tones and said reference tone falls in the middle of such sequence.

Claim 25

The communication system set forth in claim 15, wherein the durations of the reference tone and the one control tone are substantially equal.

Claim 26

The communication system set forth in claim 15, wherein said reference tone precedes said one control tone.

Claim 27

A communication system comprising a transmitter including means for generating a sequence of a first control tone followed by a reference tone followed by a second control tone, the duration of the reference tone being at least equal to the durations of the first control tone and the second control tone, means for transmitting the sequence of tones; and a receiver including a processing circuit for receiving the transmitted signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being equal to the duration of the reference tone so as to cause the reference tone in one sequence to be in time coincidence with the first control tone in the other sequence and to cause the reference tone in the other sequence to be in time coincidence with the second control tone in the one sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides a sequence of two low-frequency mixed signals, the frequencies of the low-frequency mixed signals being respectively representative of the frequencies of the control tones minus the frequency of the reference tone, and utilization means coupled to said mixing means for using the mixed signal.

Claim 28

A communication system comprising a transmitter including means for generating a sequence of a first control tone followed by a reference tone followed by a second control tone, the duration of the reference tone being at least equal to the durations of the first control tone and the second control tone, means for transmitting the sequence of tones; and a receiver including a processing circuit for receiving the transmitted signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being equal to the duration of the reference tone so as to cause the reference tone in one sequence to be in time coincidence with the first control tone in the other sequence and to cause the reference tone in the other sequence to be in time coincidence with the second control tone in the one sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides a sequence of two low-frequency mixed signals, the frequencies of the low-frequency mixed signals being respectively representative of the frequencies of the control tones minus the frequency of the reference tone, and utilization means coupled to said mixing means for using the mixed signal.

Claim 29

The communication system set forth in claim 22, wherein the duration of the first control tone is substantially equal to the duration of the second control tone.

Claim 30

The communication system set forth in claim 22, wherein the duration of the reference tone is substantially equal to the duration of the first control tone and to the duration of the second control tone.

Claim 31

The communication system set forth in claim 22, wherein each control tone has the same duration.

Claim 32

A communication system comprising a transmitter including means for generating a sequence of a first series of control tones followed by a reference tone followed by a second series of control tones, the duration of the reference tone being no less than the combined durations of the control tones in each series, and means for transmitting the sequence of tones; and a receiver including a processing circuit for receiving the transmitted signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being equal to the duration of the reference tone so as to cause the reference tone in one sequence to be in time coincidence with at least a portion of each control tone in the other sequence and to cause the reference tone in the other sequence to be in time coincidence with at least a portion of each control tone in the one sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides a sequence of low-frequency mixed signals corresponding in number to the number of control tones, The frequencies of the low-frequency mixed signals being respectively representative of the frequencies of the control tones minus the frequency of the reference tone, and utilization means coupled to said mixing means for using the mixed signal.

Claim 33

A communication system comprising a transmitter including means for generating a sequence of a first series of control tones followed by a reference tone followed by a second series of control tones, the duration of the reference tone being no less than the combined durations of the control tones in each series, and means for transmitting the sequence of tones; and a receiver including a processing circuit for receiving the transmitted signals and providing an undelayed sequence of tones, delay means coupled to said processing circuit for providing a delayed sequence of tones, the delay being equal to the duration of the reference tone so as to cause the reference tone in one sequence to be in time coincidence with at least a portion of each control tone in the other sequence and to cause the reference tone in the other sequence to be in time coincidence with at least a portion of each control tone in the one sequence, mixing means having two inputs respectively coupled to said processing circuit and to said delay means for mixing the undelayed sequence and the delayed sequence, whereby said mixing means provides a sequence of low-frequency mixed signals corresponding in number to the number of control tones, The frequencies of the low-frequency mixed signals being respectively representative of the frequencies of the control tones minus the frequency of the reference tone, and utilization means coupled to said mixing means for using the mixed signal.

Claim 34

The communication system set forth in claim 26, wherein the duration of the first sequence of control tones is substantially equal to the duration of the second sequence of control tones.

Claim 35

The communication system set forth in claim 26, wherein the duration of the reference tone is substantially equal to the duration of the first sequence of control tones and to the duration of the second sequence of control tones.

Claim 36

The communication system set forth in claim 26, wherein each control tone of the first and second sequences of control tones has substantially the same duration.

Claim 37

In a transmitter including means for generating a carrier wave, means for modulating a sequence of tones onto the carrier wave, a power supply for energizing the carrier wave generating means and the modulating means, and an encoder for generating the sequence of tones, said encoder comprising manually operable actuating means, electronic switching means coupled to said actuating means and responsive to actuation thereof to become latched on for producing an enabling signal extending indefinitely beyond release of said actuating means, the power supply being coupled to said electronic switching means and responsive to the enabling signal therefrom to produce power for energizing the carrier wave generating means and the modulating means, clock oscillator means coupled to said electronic switching means and responsive to the enabling signal therefrom for producing an oscillatory signal, a sequential switch having a control input coupled to said electronic switching means and having a plurality of tone inputs and a tone output and a reset output, said sequential switch including means responsive to an oscillatory signal on said control input sequentially to couple said tone inputs to said tone output, said sequential switch further including means responsive to the last tone input being coupled to said tone output to produce a reset signal on said reset output, said electronic switching means being coupled to said reset output and being responsive to the reset signal therefrom to interrupt said enabling signal, and a plurality of tone oscillators respectively coupled to the tone inputs of said sequential switch.

Claim 38

In a transmitter including means for generating a carrier wave, means for modulating a sequence of tones onto the carrier wave, a power supply for energizing the carrier wave generating means and the modulating means, and an encoder for generating the sequence of tones, said encoder comprising manually operable actuating means, electronic switching means coupled to said actuating means and responsive to actuation thereof to become latched on for producing an enabling signal extending indefinitely beyond release of said actuating means, the power supply being coupled to said electronic switching means and responsive to the enabling signal therefrom to produce power for energizing the carrier wave generating means and the modulating means, clock oscillator means coupled to said electronic switching means and responsive to the enabling signal therefrom for producing an oscillatory signal, a sequential switch having a control input coupled to said electronic switching means and having a plurality of tone inputs and a tone output and a reset output, said sequential switch including means responsive to an oscillatory signal on said control input sequentially to couple said tone inputs to said tone output, said sequential switch further including means responsive to the last tone input being coupled to said tone output to produce a reset signal on said reset output, said electronic switching means being coupled to said reset output and being responsive to the reset signal therefrom to interrupt said enabling signal, and a plurality of tone oscillators respectively coupled to the tone inputs of said sequential switch.

Claim 39

In the transmitter of claim 30, wherein said electronic switching means includes first and second NOR devices each having a pair of inputs and an output, the inputs of said first NOR device being respectively coupled to said manually operable actuating means and to the output of said second NOR device, the inputs of said second NOR device being coupled respectively to the output of said first NOR device and the reset output of said sequential switch, the output of said first NOR device being coupled to said clock oscillator means and the output of said second NOR device being coupled to the power supply.

Claim 40

In the transmitter of claim 30, wherein said clock oscillator means produces an oscillatory signal in the form of a series of pulses.

Claim 41

In the transmitter of claim 30, and further comprising indicator means coupled to said sequential switch and responsive to the sequential switching of said tone inputs with respect to said tone output to furnish an alerting signal.