SEQUENTIAL TONE SELECTIVE CALLING COMMUNICATION SYSTEM AND COMPONENTS THEREOF

• US 3,613,004 A
• Filed: 03/09/1964
• Issued: 10/12/1971
• Est. Priority Date: 03/09/1964
• Status: Expired due to Term

• Current Assignee: Keith H. Wycoff
• Original Assignee: Keith H. Wycoff
• Inventors: Wycoff, Keith H.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US04/350,163
• Time in Patent Office: 2,773 Days
• Field of Search: 325/55,64,51,392,466,478 340/171,223,311,171PF,170 343/225,226,288,177 331/60,76,51,50
• US Class Current: 340/7.2
• CPC Class Codes: H04W 88/188 using frequency address codes

Abstract

1. In a communication system for selectively transmitting carrier signals carrying a control tone and a call-indicator tone and intelligence from a transmitter to at least one selected receiver, the combination comprising a transmitter including a tone-generating circuit for generating a preselected control tone, means for generating a call-indicator tone, a modulating circuit for modulating the carrier signals in accordance with the control tone and the control-indicator tone and the intelligence to be transmitted, a transmitter output circuit coupled to said modulating circuit for transmitting the carrier signals including the control tone and the call-indicator tone and the intelligence to be transmitted, a receiver including an input circuit for receiving the signals from said transmitter, a detecting circuit coupled to said input circuit for detecting the control tone and the call-indicator tone and the intelligence in the signals, an audio circuit for converting the intelligence into sound waves, a coupling circuit coupling said detecting circuit to said audio circuit for coupling the intelligence and the control tone thereto, a squelch circuit coupled to said coupling circuit and operative in a first condition thereof to render said coupling circuit inoperative and operative in a second condition thereof to render said coupling circuit operative, a first control circuit coupled to said squelch circuit and responsive to the application of the carrier signals to said receiver for generating a first control signal, a second tone control circuit coupled to said squelch circuit and responsive to the application of the control tone to said receiver for generating a second control signal, and squelch circuit being responsive to the application thereto of said first and second control signals for actuating said squelch circuit from the first condition thereof into the second condition thereof to render said coupling circuit operative to pass the call-indicator tone therethrough, means for maintaining said squelch circuit in the second condition thereof until the removal of said first control signal therefrom, a third tone control circuit coupled to said coupling circuit and responsive to the application thereto of the call-indicator tone from said coupling circuit for producing an output from said third tone control circuit, and a call-indicator annunciator coupled to said third control circuit and actuated by the output therefrom, whereby said receiver is operative to operate said call-indicator annunciator upon the application thereto of both the control tone and the call-indicator tone from said transmitter, the removal of said first control signal from said squelch circuit changing said squelch circuit from the second condition thereof to the first condition thereof to render said coupling circuit inoperative. 16. A communication system comprising: TRANSMITTER FOR TRANSMITTING A SIGNAL INCLUDING A RADIO FREQUENCY CARRIER, MODULATING MEANS FOR MODULATING SAID CARRIER, CONTROL MEANS FOR INITIATING THE OPERATION OF SAID MODULATION MEANS FOR FIRST CAUSING SAID MODULATION MEANS TO MODULATE SAID CARRIER WITH A FIRST FREQUENCY SIGNAL FOR A TIME PERIOD OF PREDETERMINED LIMITED DURATION AND FOR IMMEDIATELY THEREAFTER CAUSING SAID MODULATION MEANS TO MODULATE SAID CARRIER WITH A DIFFERENT FREQUENCY SIGNAL TO THEREBY CAUSE SAID TRANSMITTER MEANS TO FIRST TRANSMIT SAID CARRIER MODULATED BY A BURST OF SAID FIRST FREQUENCY SIGNAL AND THEN TRANSMIT SAID CARRIER MODULATED BY A SECOND FREQUENCY SIGNAL, A RECEIVER INCLUDING MEANS FOR RECEIVING AND DEMODULATING THE SIGNAL TRANSMITTED FROM SAID TRANSMITTER TO PROVIDE AN OUTPUT INCLUDING SAID BURST OF SAID FIRST FREQUENCY SIGNAL FOLLOWED BY SAID SECOND FREQUENCY SIGNAL, A NORMALLY OPERATIVE FIRST DECODING CIRCUIT MEANS AND A NORMALLY INOPERATIVE SECOND DECODING CIRCUIT MEANS EACH CONNECTED TO BE SUPPLIED WITH SAID OUTPUT AND A UTILIZATION CIRCUIT MEANS CONTROLLED BY SAID SECOND DECODING CIRCUIT MEANS, SAID FIRST DECODING CIRCUIT MEANS HAVING MEANS RESPONSIVE TO SAID BURST OF SAID FIRST FREQUENCY SIGNAL IN THE OUTPUT FROM SAID RECEIVER FOR RENDERING SAID SECOND DECODING CIRCUIT OPERATIVE FOR A TIME PERIOD OF PREDETERMINED LIMITED DURATION OVERLAPPING THE TIME DURING WHICH SAID OUTPUT INCLUDES SAID SECOND FREQUENCY SIGNAL, SAID SECOND DECODING CIRCUIT MEANS HAVING MEANS RESPONSIVE TO SAID SECOND FREQUENCY SIGNAL IN THE OUTPUT OF SAID RECEIVER FOR CAUSING ENERGIZATION OF SAID UTILIZATION CIRCUIT MEANS.

Claims

1. In a communication system for selectively transmitting carrier signals carrying a control tone and a call-indicator tone and intelligence from a transmitter to at least one selected receiver, the combination comprising a transmitter including a tone-generating circuit for generating a preselected control tone, means for generating a call-indicator tone, a modulating circuit for modulating the carrier signals in accordance with the control tone and the control-indicator tone and the intelligence to be transmitted, a transmitter output circuit coupled to said modulating circuit for transmitting the carrier signals including the control tone and the call-indicator tone and the intelligence to be transmitted, a receiver including an input circuit for receiving the signals from said transmitter, a detecting circuit coupled to said input circuit for detecting the control tone and the call-indicator tone and the intelligence in the signals, an audio circuit for converting the intelligence into sound waves, a coupling circuit coupling said detecting circuit to said audio circuit for coupling the intelligence and the control tone thereto, a squelch circuit coupled to said coupling circuit and operative in a first condition thereof to render said coupling circuit inoperative and operative in a second condition thereof to render said coupling circuit operative, a first control circuit coupled to said squelch circuit an responsiVe to the application of the carrier signals to said receiver for generating a first control signal, a second tone control circuit coupled to said squelch circuit and responsive to the application of the control tone to said receiver for generating a second control signal, and squelch circuit being responsive to the application thereto of said first and second control signals for actuating said squelch circuit from the first condition thereof into the second condition thereof to render said coupling circuit operative to pass the call-indicator tone therethrough, means for maintaining said squelch circuit in the second condition thereof until the removal of said first control signal therefrom, a third tone control circuit coupled to said coupling circuit and responsive to the application thereto of the call-indicator tone from said coupling circuit for producing an output from said third tone control circuit, and a call-indicator annunciator coupled to said third control circuit and actuated by the output therefrom, whereby said receiver is operative to operate said call-indicator annunciator upon the application thereto of both the control tone and the call-indicator tone from said transmitter, the removal of said first control signal from said squelch circuit changing said squelch circuit from the second condition thereof to the first condition thereof to render said coupling circuit inoperative.

2. In a communication system for selectively transmitting intelligence from a transmitter to at least one selected receiver, a transmitter comprising a stable fixed-frequency oscillator for generating a first signal having a predetermined frequency, a nonoscillating-frequency divider coupled to said fixed-frequency oscillator for generating a plurality of control tones that are subharmonics of said first signal, a switching circuit coupled to said frequency divider for automatically changing the frequency division thereof to produce two or more preselected control tones in a predetermined order to provide a series of control tones, an output circuit coupled to said frequency divider for transmitting signals corresponding to the series of tones generated thereby and the intelligence to be transmitted, a source of operating potential for said fixed-frequency oscillator continually connected thereto so that said fixed-frequency oscillator is continuously operating at a stable operating frequency during the use of said transmitter, and a transmission control circuit coupled to said output circuit for applying operating potential thereto to effect transmission by said transmitter.

3. In a communication system for selectively transmitting signals including at least two control tones and intelligence from a transmitter to at least one selected receiver, a receiver comprising an input circuit for receiving signals from an associated transmitter, a detecting circuit coupled to said input circuit for detecting the control tone and the intelligence in the signals, a translating circuit coupled to said detecting circuit for translating the intelligence into a usable form, a squelch circuit coupled to said translating circuit and operative in a first condition thereof to render said translating circuit inoperative and operative in a second condition thereof to render said translating circuit operative, a first tone control circuit having an input coupled to said detecting circuit an having an output, a normally inoperative second tone control circuit having an input coupled to the output of said first tone control circuit and having an output coupled directly to said squelch circuit, said first tone control circuit being responsive to the application thereto and the subsequent removal therefrom of the first control tone for actuating said second tone control circuit from the inoperative condition to the operative condition thereof, said second tone control circuit being responsive to the application thereto and the subsequent removal therefrom of the second control tone when in the operatIve condition thereof for actuating said squelch circuit from the first condition thereof to the second condition thereof to render said translating circuit operative.

4. In a communication system for selectively transmitting signals including a series of control tones and intelligence from a transmitter to at least one selected receiver, a receiver comprising an input circuit for receiving signals from an associated transmitter, a detecting circuit coupled to said input circuit for detecting the control tones and the intelligence in the signals, a translating circuit coupled to said detecting circuit for translating the intelligence into a usable form, a squelch circuit coupled to said translating circuit and operative in a first condition thereof to render said translating circuit inoperative and operative in a second condition thereof to render said translating circuit operative, a plurality of tone control circuits corresponding in number to the control tones in the series of control tones, each of said tone control circuits having an input coupled to said detecting circuit and having an output, the second and each succeeding tone control circuit having an inoperative condition and an operative condition, the first tone control circuit having the output thereof coupled to said second control circuit and the second and each succeeding tone control circuit having the output thereof connected to the next tone control circuit, said first tone control circuit being responsive to the application thereto and the subsequent removal therefrom of the corresponding control tone for actuating said second control tone circuit from the inoperative condition to the operative condition thereof and the second and each succeeding tone control circuit being responsive to the application thereto and the subsequent removal therefrom of the corresponding control tone when in the operative condition thereof for actuating the next tone control circuit from the inoperative condition to the operative condition thereof and the last tone control circuit being responsive to the application thereto and the subsequent removal therefrom of the corresponding control tone when in the operative condition thereof for generating a control signal, and means for applying the control signal to said squelch circuit, the application of said control signal to said squelch circuit actuating said squelch circuit from the first condition thereof to the second condition thereof, thereby to render said translating circuit operative.

5. In a communication system for selectively transmitting carrier signals carrying a control tone and intelligence from a transmitter to at least one selected receiver, a receiver comprising an input circuit for receiving signals from an associated transmitter, a detecting circuit coupled to said input circuit for detecting the control tones and the intelligence in the signals, a translating circuit coupled to said detecting circuit for translating the intelligence into a usable form, a squelch circuit coupled to said translating circuit and operative in a first condition thereof to render said translating circuit inoperative and operative in a second condition thereof to render said translating circuit operative, a carrier control circuit coupled to said detecting circuit and responsive to the application of on-frequency carrier signals to said receiver for generating a first control signal, a switching circuit coupled to said detecting circuit and responsive to the application of off-frequency carrier signals to said receiver for generating a second control signal, a tone control circuit coupled to said detecting circuit and responsive to the application thereto of the control tone for generating a third control signal, means for applying said first control signal and said second control signal and said third control signal to said squelch circuit, the application of both said first control signal and said third control signal in the absence of said second control signal to said sqUelch circuit actuating said squelch circuit from the first condition thereof to the second condition thereof, thereby to render said translating circuit operative, the removal of said first control signal from said squelch circuit actuating said squelch circuit from the second condition thereof to the first condition thereof, thereby to render said translating circuit inoperative.

6. In a communication system for selectively transmitting carrier signals carrying a series of two control tones each of finite duration and intelligence from a transmitter to at least one selected receiver, said receiver comprising an input circuit for receiving the signals from an associated transmitter, a detecting circuit coupled to said input circuit to provide detected signals including the series of control tones and the intelligence, an audio circuit coupled to said detecting circuit for converting the detected signals into sound waves, a squelch circuit coupled to said audio circuit and operative in a first condition thereof to render said audio circuit inoperative and operative in a second condition thereof to render said audio circuit operative, a first control tone circuit having an input for receiving the detected signals and having an output, said first control tone circuit being responsive to the application thereto of the first control tone for producing at the output thereof a gating pulse occurring at least partly during the initial portion of the second control tone, a normally inoperative second control tone circuit having a first input for receiving the detected signals and having a second input coupled to the output of the first control tone circuit and having an output coupled to said squelch circuit, said second control tone circuit being rendered operative by the application thereto of the gating pulse and being responsive to a second control tone received while said second control tone circuit is operative to produce an output signal, said second control tone circuit being responsive to the termination of said output signal to produce at the output thereof a control signal, said control signal actuating said squelch circuit from the first condition thereof to the second condition thereof to render said audio circuit operative to produce sound waves in response to the detected signals, and means responsive to said output signal for maintaining said second control tone circuit operative for the duration of the second control tone to delay production of said control signal until termination of the second control tone, thereby to prevent the control tones from being converted into sound waves.

7. In a communication system for selectively transmitting carrier signals carrying a series of control tones each of finite duration and intelligence from a transmitter to at least one selected receiver, said receiver comprising an input circuit for receiving the signals from an associated transmitter, a detecting circuit coupled to said input circuit to provide detected signals including the series of control tones and the intelligence, an audio circuit coupled to said detecting circuit for converting the detected intelligence into sound waves, a squelch circuit coupled to said audio circuit and operative in a first condition thereof to render said audio circuit inoperative and operative in a second condition thereof to render said audio circuit operative, a plurality of control tone circuits corresponding in number to the control tones and each having an input for receiving the detected signals and each having an output, the first of said control tone circuits having the output thereof coupled to said second control tone circuit and the second and each succeeding control tone circuit having the output thereof coupled to the next succeeding one of said control tone circuits, said first control tone circuit being responsive to the application thereto of the first control tone for producing at the output thereof a gating pulse occurring at least partly during the initial portion of the second control tone, the second and each succeeding one of said control tone circuits being normally inoperative and being rendered operative by the application thereto of the gating pulse from the next preceding control tone circuit and being responsive to the associated control tone received while the associated control tone circuit is operative to produce at the output thereof a gating pulse occurring at least partly during the initial portion of the associated control tone, the last of said control tone circuits being rendered operative by the application thereto of the gating pulse from the next preceding control tone circuit and being responsive to the last control tone received while said last control tone circuit is operative to produce at the output thereof an output signal terminating prior to the termination of the last control tone, said last control tone circuit being responsive to the termination of said output signal to produce at the output thereof a control signal, means for applying said control signal to said squelch circuit for actuating said squelch circuit from the first condition thereof to the second condition thereof to render said audio circuit operative to produce sound waves in response to the detected signals, and means responsive to said output signal for maintaining said last control tone circuit operative for the duration of the last control tone to delay production of said control signal until termination of the last control tone, thereby to prevent the control tones from being converted into sound waves.

8. The receiver set forth in claim 7, wherein the gating pulses from said control tone circuits respectively commence substantially at the same time that the associated control tone terminates and the output.

9. The receiver set forth in claim 7, wherein the duration of each of said gating pulses is substantially shorter than the duration of the associated control tone to minimize the possibility of said audio circuit being rendered operative in response to control tones other than those to which the control tone circuits are respectively tuned.

10. The receiver set forth in claim 7, wherein the input of each of said control tone circuits is coupled to said detecting circuit.

11. In a communicating system for selectively transmitting intelligence from a transmitter to at least one selected receiver, the combination comprising a transmitter including a tone-generating circuit for generating a plurality of control tones, a first tone selector for coupling to said tone-generating circuit to preselect a first control tone to be transmitted, a second tone selector for coupling to said tone-generating circuit to preselect a second control tone to be transmitted, an electronic tone switching and timing circuit for automatically sequentially coupling said selectors to said tone-generating circuit to produce a series of the two preselected tones each with a finite duration, said tone switching and timing circuit substantially immediately switching from the first control tone in the series of preselected tones to the second control tone in the series of preselected tones, and a transmitter output circuit coupled to said tone-generating circuit for transmitting signals carrying the series of two control tones and the intelligence to be transmitted;

and a receiver including an input circuit for receiving the signals from said transmitter, a detecting circuit coupled to said input circuit to provide detected signals including the series of control tones and the intelligence, a translating circuit coupled to said detecting circuit for converting the detected intelligence into a usable form, a squelch circuit coupled to said translating circuit and operative in a first condition thereof to render said translating circuit inoperative and operative in a second condition thereof to render said translating circuit operative, a first electrical filter for receiving the detected signals and operative to produce an output in response to a control tone having a frequency lying within a first band of frequencies containing the frequency of the first control tone, a first tone output circuit having an input coupled to said first electrical filter and having an output, said first tone output circuit being responsive to the application thereto of the first control tone for producing at the output thereof a gating pulse occurring at least partly during the initial portion of the second control tone and having a duration substantially shorter than the second control tone, a second electrical filter coupled to said input circuit and operative to produce an output in response to a control tone having a frequency lying within a second band of frequencies containing the frequency of the second control tone, a normally inoperative second tone output circuit having a first input for receiving the detected signals and having a second input coupled to the output of said first tone output circuit and having an output, said second tone output circuit being rendered operative by the application thereto of the gating pulse and being responsive to a second control tone received while said second control tone circuit is operative to produce an output signal, a reference circuit for providing a reference signal for said tone output circuits and operative to permit production of a gating pulse by said first tone output circuit only in response to a first control tone having a frequency lying within a band of frequencies narrower than said first band of frequencies and operative to permit production of said output signal by said second tone output circuit only in response to a second control tone having a frequency lying within a band of frequencies narrower than said second band of frequencies, and means responsive to said output signal to provide a control signal for actuating said squelch circuit from the first condition thereof to the second condition thereof to render said translating circuit operative to convert the detected intelligence into a usable form.

12. In a communication system for selectively transmitting intelligence from a transmitter to at least one selected receiver, the combination comprising a transmitter including a tone-generating circuit for generating a plurality of control tones, at least two tone selectors for individual coupling to said tone-generating circuit to preselect a series of control tones to be transmitted, an electronic tone switching and timing circuit for automatically sequentially coupling said selectors to said tone-generating circuit to produce a series of preselected tones each with a finite duration, said tone switching and timing circuit substantially immediately switching from the next preceding control tone in the series of preselected tones to the next succeeding control tone in the series of preselected tones, and a transmitter output circuit coupled to said tone-generating circuit for transmitting signals carrying the series of control tones and the intelligence to be transmitted;

and a receiver including an input circuit for receiving the signals from said transmitter, a detecting circuit coupled to said input circuit to provide detected signals including the series of control tones and the intelligence, a translating circuit coupled to said detecting circuit for converting the detected intelligence into a usable form, a squelch circuit coupled to said translating circuit and operative in a first condition thereof to render said translating circuit inoperative and operative in a second condition thereof to render said translating circuit operative, a plurality of electrical filters corresponding in number to the control tones for receiving the detected signals and each being operative to produce an output in response to a control tone having a frequency lying within a band of frequencies containing the frequency of the control tone to which the associated filter is tuned, a plurality of tone output circuits corresponding in number to said electrical filters and each having an input cOupled to the associated one of said electrical filters and each having an output, the first of said tone output circuits having the output thereof coupled to said second tone output circuit and the second and each succeeding tone output circuit having the output thereof coupled to the next succeeding one of said tone output circuits, said first tone output circuit being responsive to the application thereto of the first control tone for producing at the output thereof a gating pulse occurring at least partly during the initial portion of the second control tone and having a duration substantially shorter than the duration of the second control tone, the second and each succeeding one of said tone output circuits being normally inoperative and being rendered operative by the application thereto of the gating pulse from the next preceding tone output circuit and being responsive to the associated control tone received while the associated tone output circuit is operative to produce at the output thereof a gating pulse occurring at least partly during the initial portion of the associated control tone and having a duration substantially shorter than the associated control tone, the last of the tone output circuits being rendered operative by the application thereto of the gating pulse from the next preceding tone output circuit and being responsive to the last control tone received while said last control tone circuit is operative to produce at the output thereof an output signal, a reference circuit for providing a reference signal for said tone output circuits and operative to permit production of a gating pulse by said tone output circuits only in response to an associated control tone having a frequency lying within a band of frequencies narrower than the associated band of frequencies and operative to permit production of said output signal by the last of said tone output circuits only in response to an associated control tone having a frequency lying within a band of frequencies narrower than the associated band of frequencies, and means responsive to said output signal to provide a control signal for actuating said squelch circuit from the first condition thereof to the second condition thereof to render said translating circuit operative to convert the detected intelligence into a usable form.

13. The combination set forth in claim 12, wherein the duration of the series of control tones transmitted by said transmitter is no longer than on the order of 250 milliseconds.

14. The combination set forth in claim 12, wherein the gating pulse from each of said tone output circuits commences at the same time that the associated control tone terminates.

15. In a communication system for selectively transmitting intelligence from a transmitter to at least one selected receiver, the combination comprising a transmitter including a tone-generating circuit for generating a plurality of control tones, at least two tone selectors for individual coupling to said tone-generating circuit to preselect a series of control tones to be transmitted, an electronic tone switching and timing circuit for automatically sequentially coupling said selectors to said tone-generating circuit to produce a series of preselected tones each with a finite duration, a transmitter output circuit coupled to said tone-generating circuit for transmitting signals carrying the series of control tones and the intelligence to be transmitted, and means for rendering said electronic tone switching and timing circuit operative to cause said tone-generating circuit to produce a series of preselected control tones and for simultaneously rendering said transmitter output circuit operative to transmit both the series of control tones and the intelligence;

and a receiver including an input circuit for receiving the signals from said transmitter, a detecting circuit coupled to said input circuit for detecting the control tones and the intelligence in the signals, a translating circuit coupled to said detecting circuIt for translating the intelligence into a usable form, a squelch circuit coupled to said translating circuit and operative in a first condition thereof to render said translating circuit inoperative and operative in a second condition thereof to render said translating circuit operative, a carrier control circuit coupled to said detecting circuit and responsive to the application of the carrier signals to said receiver for generating a first control signal, a tone control circuit coupled to said detecting circuit and responsive to the application thereto and the subsequent removal therefrom of the series of control tones for generating a second control signal, means for applying said first control signal and said second control signal to said squelch circuit, this application of both said first control signal and said second control signal to said squelch circuit actuating said squelch circuit from the first condition thereof to the second condition thereof, thereby to render said translating circuit operative, and means for maintaining said squelch circuit in the second condition thereof upon the removal of said second control signal therefrom so long as said first control signal is applied thereto, the removal of said first control signal from said squelch circuit actuating said squelch circuit from the second condition thereof to the first condition thereof, thereby to render said translating circuit inoperative.