Communication system

• US 4,066,964 A
• Filed: 01/06/1967
• Issued: 01/03/1978
• Est. Priority Date: 01/06/1967
• Status: Expired due to Term

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: Wheatley, Charles E. III, Moore, Charles R., Franklin, Peter G., Israel, Jack D., Costanza, Samuel T., Gebhardt, Frank L.
• Primary Examiner(s): Birmiel, Howard A.
• Application Number:
  US04/607,854
• Time in Patent Office: 4,015 Days
• Field of Search: 325/17, 325/30, 325/31, 325/33, 325/35, 325/40, 325/53, 325/55, 325/58, 325/63, 325/64, 325/131, 325/154, 325/163, 340/351, 340/171 PP, 340/174, 340/171 PF, 340/146.1 BA, 179/15.55, 343/204
• US Class Current: 375/260
• CPC Class Codes: H04B 7/24 for communication between two or more posts wireless communication networks H04W
• CPC Class Codes: H04K 1/003 by varying carrier frequency at or within predetermined or random intervals H04K1/04 takes precedence

Abstract

This invention relates to a communication system wherein a plurality of stations can communicate with each other, without going through a central switchboard; and more particularly to such a communication system that is as private as possible -- the commmunication system having, in addition, the capability of conference calls and a command-override.

Claims

1. A communication system comprising:

A. a plurality of stations, selected said stations comprising a receiver, and at least one station comprising a transmitter;

B. means for varying the frequency of each receiver so that each receiver frequency-hops in an individual frequency-hopping sequence, said individual frequency-hopping sequence defining each individual receiver'"'"'s address;

C. means for generating a transmitter carrier-wave that frequency-hops in the individual frequency-hopping sequence of any selected receiver, said means defining the transmitter'"'"'s ability to address a transmission to any selected receiver;

D. means for varying the receiver-frequency, so that the receiver searches for a transmission addressed to said receiver;

E. means for stabilizing the receiver-frequency of said receiver, when said receiver finds a transmission addressed to it, to synchronize said receiver operation to said transmission;

F. means for producing a synchronizing-signal at said transmitter and for impressing said synchronizing-signal onto said addressed frequency-hopping carrier wave; and

G. means, activated at the receiver by said synchronizing-signal, for producing an activating-signal that synchronizes the receiver'"'"'s operation to said synchronizing-signal.

2. The combination of claim 1 including

means for varying the frequency-hopping sequence of each station to periodically monitor a chosen frequency-hopping sequence to determine whether a special signal is being broadcast.

3. The combination of claim 1 including

means for terminating, at said receiver, the impressing of said synchronizing signals onto said frequency-hopping carrier-wave;

means, at said transmitter, for generating and impressing a data-signal onto said addressed frequency-hopping carrier wave; and

means, at said receiver, for recovering the data in said data-signal.

4. The combination of claim 3 including

means for impressing said data-signal onto said addressed frequency-hopping carrier-wave in a redundancy manner;

and

means, at said receiver, for recovering the data in said redundanced data-signal.

5. The combination of claim 4 including

means, at said receiver, for producing signal-to-noise ratio signals for selected portions of said redundanced data-signal;

and

means, at said receiver, for selecting optimal portions of said redundanced data-signal in accordance with said signal-to-noise ratio signals.

6. The combination of claim 3 including

means, at said transmitter, for impressing said synchronizing-signal and said data-signal onto said addressed frequency-hopping carrier-wave in the form of bi-phase modulation;

and

means, at said receiver, for demodulating said bi-phase modulation.

7. The combination of claim 1 including

means for producing a chosen frequency-hopping sequence to indicate that a special transmission is to be broadcast.

8. The combination of claim 1 including

means for converting said synchronizing-signal into a biphase synchronizing-signal;

means for impressing said biphase synchronizing-signal onto said frequency-hopping carrier-wave for a finite interval;

means for producing a data-signal;

means for converting said data-signal into a biphase data-signal; and

means for impressing said biphase data-signal onto said frequency-hopping carrier-wave after the termination of said finite interval.

9. The combination of claim 1 including means for converting said synchronizing-signal and said data-signal to a Non Return To Zero Mark system.

10. The combination of claim 1 wherein said synchronizing-signal comprises a start-code, an intermediate-code, and an end-code, said synchronizing-signal occupies the live-portion of said frame-period;

means for transmitting said synchronizing-signal a given number of times, defining a synchronizing-signal interval;

means for producing data-signals;

means for redundancing said data-signals, said redundancing means comprising means for dividing said data-signals into sub-words, and interlacing said sub-words into the live-portion of successive frames;

means for transmitting said redundanced data-signals after the termination of said synchronizing-signal interval.

11. The combination of claim 10, wherein said redundancing means comprises a plurality of registers;

means for storing one sub-word in one register;

means for transmitting said sub-word as a portion of one frame, and circulating said sub-word to a subsequent register; and

means for transmitting said sub-word as a different portion of a subsequent frame.

12. A communication system comprising:

A. a plurality of stations, selected said stations comprising a receiver, and at least one station comprising a transmitter;

B. means for varying the frequency of each receiver so that each receiver frequency-hops in an individual frequency-hopping sequence, said individual frequency-hopping sequence defining each individual receiver'"'"'s address;

C. means for generating a transmitter carrier-wave that frequency-hops in the individual frequency-hopping sequence of any selected receiver, said means defining the transmitter'"'"'s ability to address a transmission to any selected receiver;

D. means for varying the receiver-frequency, so that the receiver searches for a transmission addressed to said receiver;

E. means for stabilizing the receiver-frequency of said receiver, when said receiver finds a transmission addressed to it, to synchronize said receiver operation to said transmission;

F. means for producing a synchronizing-signal at said transmitter and for impressing said synchronizing-signal onto said addressed frequency-hopping carrier wave;

G. means, activated at the receiver by said synchronizing-signal, for producing an activating-signal that synchronizes the receiver'"'"'s operation to said synchronizing-signal;

a. means, energized by said activating-signal for producing a coarse-synchronizing signal for coarse-synchronizing said receiver'"'"'s operation to said synchronizing-signal;

b. means, energized by said activating-signal for producing a bit-synchronizing signal that bit-synchronizes said receiver'"'"'s operation to said synchronizing signal; and

c. means, energized by said activating-signal, for producing a word-synchronizing signal that word-synchronizes said receiver'"'"'s operation to said synchronizing-signal.

13. In a communications system wherein information is transmitted in the form of digitally coded bits of modulated carrier, said bits generated at a bit rate, said information being transmitted in a number of successive frames including a plurality of synchronizing frames, each said synchronizing frame comprising a start-code portion and an end-code portion, and wherein the frequency of the transmitted carrier is shifted from frame to frame in a selected predetermined frequency shifting sequence that identified a unique receiver address;

receiver searching and synchronization circuitry comprising

means for generating a receiver-waveform having a frequency shifting sequence identifying the receiver,

means for effecting a predetermined phase difference of a first sense of the receiver-waveform with respect to the received-waveform,

receiver searching means for progressively varying the receiver frequency to shift said receiver-waveform phase in a second sense with respect to said received waveform for achieving partial coincidence of said received and receiver-waveforms,

coarse synchronization means for determining partial coincidence of said received and receiver-waveforms for at least portions of a group of frames,

means responsive to detection of said coarse synchronization for terminating the receiver searching,

means responsive to the detection of coarse synchronization for achieving bit-synchronization of individual bits, said bit synchronization means comprising means for generating a train of receiver clock-pulse bits, means for comparing the phase of the train of bits of the transmitted information signal with the phase of the train of receiver bits, and

means responsive to the phase comparison for varying the phase of the receiver clock-pulse bit generator in a sense to minimize the detected phase difference between transmitted and receiver bit trains, and

means responsive to bit synchronization for effecting word synchronization to fully align transmitted frames with receiver frames, said word-synchronizing means comprising

means for storing a start-code and an end-code in the receiver, each code uniquely identifying the start-code portion and end-code portion of each transmitted synchronizing signal frame,

means for comparing incoming signals with the stored codes to detect occurrence of the start-code portion, and means for indicating word synchronization upon detection of such occurrence, means responsive to detection of lack of occurrence of the start code portion for subsequently comparing the incoming signal with both start and end codes stored in the receiver,

means responsive to detection of a start-code portion in the second mentioned comparison for retarding receiver frame shifting sequence for a predetermined interval substantially equal to the interval of the start-code portion, and

means responsive to detection of the end-code portion in the incoming signal during the second mentioned comparison for advancing the receiver frame shifting sequence by a predetermined interval substantially equal to the duration of the end-code portion.

14. In a communication system wherein information is transmitted and received as a waveform having a number of successive frames, said frames each comprising a unique frequency, with the frequency of the transmitted waveform being shifted from frame to frame in a selected predetermined frequency shifting sequence that identifies a unique receiver address, a receiver comprising:

A. means for generating a receiver-waveform that comprises a series of frequency-sensitive receiving-frames that are frequency shifted in the selected frequency shifting sequence that identifies a receiver;

B. means for determining partial coincidence of said received waveform and said receiver-waveform for at least a part of one frame;

C. means for determining the number of such partial coincidences in a group of frames;

D. means for generating a signal indicating coarse-synchronization when a predetermined number of partial coincidences has been detected in said group; and

E. means, comprising said coarse-synchronization signal, for time-wise shifting, said receiver-waveform.

15. The combination of claim 14 wherein limitation A comprises

means for generating clock pulses at a clock rate;

a timing generator, responsive to the clock pulses, for generating timing signals; and

means, comprising a code generator responsive to the time signals, for generating said receiver-waveform;

D. means for controlling the code-generator to effect searching and coarse-synchronization of the received-waveform and the receiver-waveform;

E. means for controlling the code-generator to achieve bit-synchronization of the train of bits of the receiver-waveform and the received-waveform.

F. means for controlling the code-generator to achieve word-synchronization of the receiver-waveform and the synchronization-signal portion of the received-waveform.

16. A transmitter for use in a communication system, comprising:

means for broadcasting a coded synchronizing signal having a duration of one frame period, and repetitive over a number of consecutive frame periods;

means for sending a data-signal during frame periods following said number of frame periods of said synchronizing signal;

means for generating said data-signal in sub-words, each having a duration of less than one-half of said frame period;

means for broadcasting each data-signal sub-word at least two times during each data-signal frame period; and

means for varying the transmitter-frequency, for frequency-shifting both said synchronizing signal and said data-signal in a selected predetermined frequency-shifting sequence that identifies a unique receiver address, each said frequency shift occurring at the end of a frame period.

17. In association with a communication system wherein a plurality of receivers frequency-hop in individual frequency-hopping sequences, the individual frequency-hopping sequence of each individual receiver defining each individual receiver'"'"'s address, a transmitter comprising:

means for varying the transmitter-frequency to produce a carrier-wave that frequency hops in the individual frequency-hopping sequence of any desired receiver, said means defining the transmitter'"'"'s ability to address a desired receiver, said means comprising;

a code generator;

a frequency-synthesizer;

means for applying the output of said code-generator to said frequency-synthesizer to change the output frequencies of said frequency-synthesizer in accordance with the output of said code-generator -- whereby the output of the frequency-synthesizer produces a frequency-hopping carrier wave series of successive frames with a frame-period duration;

a matrix having adjustable input-output paths;

means for applying the output of said code-generator to said matrix;

means for applying the output of said matrix to said frequency-synthesizer -- whereby adjusting said matrix causes the output frequencies of said frequency-synthesizer to produce a carrier-wave that frequency-hops in a different sequence, for addressing different receivers;

means for producing a synchronizing signal;

means for impressing said synchronizing signal onto said addressed frequency-hopping carrier-wave;

means for terminating said synchronizing signal;

means for producing a data-signal; and

means for impressing said data-signal onto said addressed frequency-hopping carrier-wave.

18. The transmitter of claim 17, including:

means for redundancing said data-signal -- whereby said addressed frequency-hopping carrier-wave has said redundanced data-signal impressed thereon.

19. The transmitter of claim 17, including:

means for converting said synchronizing-signal and said data-signal into a biphase signal -- whereby said biphase synchronizing and data-signals are impressed onto said frequency-hopping carrier-wave.

20. The combination including

means for broadcasting a coded synchronizing-signal having a duration of one frame period and repetitive over a synchronizing-signal interval having a given number of consecutive frame periods;

means for broadcasting a data-signal during frame periods following said synchronizing signal interval;

means for generating said data-signal in sub-words each having a duration of less than one-half of said frame period;

means for broadcasting at least two different data-signal sub-words during each data-signal frame period, and for broadcasting each sub-word in at least two different frame periods.

21. The combination of claim 20, including

means for varying the broadcast-frequency, for frequency-shifting both said synchronizing-signal and said data-signal in a selected predetermined frequency shifting sequence that identifies a unique receiver address, each said frequency shift occurring at the end of a frame period.

22. A transmitter comprising:

A. a timing circuit having

1. master clock means for producing pulse-signals at a given frequency;

2. means for converting said pulse-signals to a desired clock frequency;

3. means, energized by said frequency-converted pulse-signals, for producing timing-signals;

4. means for converting said pulse-signals to a modulating-signal;

B. a frequency-hopping circuit having

1. code-generator means, energized by specific timing-signals, for producing a code;

2. a matrix, having selectable input-output paths;

3. means for applying said code from said code-generator to said matrix -- whereby the output from said matrix depends upon the input signal and upon the selected input-output path;

4. frequency-synthesizing means for producing frequencies that depend upon the input signals;

24. The combination of claim 22, including

means, positioned between the combining OR circuit and the mixer, for converting a binary signal to a biphase signal, havinga phase-shift-key circuit;

2. means for applying the binary signal to said phase-shift-key circuit;

3. means for applying said modulating-signal from said timing-circuit to said phase-shift-key circuit for causing one state of the binary signal to be converted to a given phase of said modulating-signal, and causing the other state of the binary signal to be converted to the opposite phase of said modulating-signal.

26. The combination of claim 24 wherein said means for producing a frequency-hopping carrier-wave comprises

A. a timing circuit havingmaster clock means for producing pulse-signals at a given frequency;

2. means for converting said pulse-signals to a desired clock frequency;

3. clock-pulse generator means, energized by said frequency-converted pulse-signals, for producing trigger-like clock-pulses at a clock-frequency;

4. timing generator means, energized by said clock-pulses, for producing timing-signals;

B. a frequency-hopping circuit comprising;

1. code-generator means, energized by specific said timing-signals, for producing a pseudo-random code;

2. a matrix, having selectable input-output paths;

28. The combination of claim 24, wherein said redundancy means comprises:

1. a first register;

2. means for loading said encoded data-signals into said first register;

3. a first OR circuit;

4. means for unloading the contents of said first register to said first OR circuit, to combine a group of data-signals to form a sub-word of a frame;

5. a second register;

6. means for shifting the data-signal at said first OR circuit to said second register;

7. means for unloading the contents of said second register to said first OR circuit to combine said group of data-signals to form a subword of another frame;

8. a third register;

9. means for shifting the data-signal at said first OR circuit to said third register;

30. The combination of claim 24 wherein said synchronizing-signal-producing-means comprises:

1. generator means for producing a synchronizing signal having a start-code, an intermediate-code, and an end-code;

2. frame-counting means, associated with signals from said timing-circuit, for producing a first signal for the duration of said synchronizing-signal interval, and for producing a second signal at the termination of said synchronizing-signal interval.

31. The combination of claim 24 wherein said last two means comprise:

1. a synchronizing-signal gate-circuit;

2. a data-signal gate-circuit;

3. a combining OR circuit;

4. means for applying the synchronizing-signal to said synchronizing-signal gate-circuit;

5. means for applying the data-signal from the redundancing-means to the data-signal gate-circuit;

6. means for enabling said synchronizing-signal gate-circuit, and applying said synchronizing-signal to said combining OR circuit for the duration of a synchronizing-signal interval;

7. means for disabling said data-signal gate-circuit, and preventing application of said data-signal to said combining OR circuit for the duration of said synchronizing-signal interval;

37. The receiver of claim 30 wherein limitation A comprises

a code-generator;

a matrix having given input-output paths;

means for applying the output signal of said code-generator to said matrix -- whereby the output of said matrix depends upon said output signal from said code-generator and the input-output paths of said matrix;

a frequency synthesizer;

means for applying the output of said matrix to said frequency-synthesizer -- whereby the receiver produces a frequency-hopping receiver-waveform having a given frequency-hopping sequence.

38. The combination of claim 31, including

timing-circuit means for producing trigger-pulses for triggering said code-generator;

means for applying said trigger-pulses to said code-generator;

means, at said timing-circuit means, for varying the rate at which said trigger-pulses are applied to said code-generator.

39. The combination of claim 30 wherein said data is in a redundanced form, and said receiver comprises means for receiving the data in said redundanced data-signal.

41. The combination of claim 30, including

means for varying the receiver-frequency of each receiver to periodically monitor a chosen frequency-hopping sequence to determine whether a special signal is being broadcast.

46. The combination of claim 39, wherein data is available in a redundanced form, a data-recovery circuit comprising:

means for obtaining each redundanced portion of said data;

means for obtaining the signal-to-noise ratio for each redundanced portion of said data;

means for utilizing the portion of said redundanced data having optimal signal-to-noise conditions.

53. The combination of claim 46 wherein an information signal appears as a bi-phase modulation on a given waveform of a given frequency, the combination comprising:

means for doubling the frequency of said given waveform;

means, comprising an oscillator, for producing a reference waveform of the same frequency as said given waveform.

means for doubling the frequency of said reference waveform;

means, comprising a mixer, for producing an error-signal corresponding to the phase-difference between said frequency-doubled given-waveform and said frequency-doubled reference-waveform;

means for applying said error-signal to said oscillator for phase correcting said reference waveform from said oscillator to have the same phase as said given waveform.

60. The combination of claim 53, including

A. a timing-circuit havingmaster clock means for producing pulse-signals at a given frequency;

2. means for converting said pulse-signals to a desired clock frequency;

3. clock-pulse generator means, energized by said frequency-converted pulse-signals, for producing trigger-like clock-pulses at a clock-frequency, said clock-pulses appearing on a common output;

4. timing generator means, energized by said clock-pulses, for producing timing-pulses, said timing-pulses appearing at individual outputs;

5. means for applying said specific timing-signals to said shift-signal terminal of said code-generator.

23. means for applying the output of said matrix to said frequency-synthesizer -- whereby the instantaneous output frequency of said frequency-synthesizer depends upon the instantaneous code and the selected input-output path of said matrix, and said frequency-synthesizer produces a carrier-wave having successive frames at different frequencies, a selected set of matrix input-output paths causing said frequency-synthesizer to produce an output that frequency-hops in the same sequence as an addressed station;

C. means for converting input data to a data-signal;

D. redundancing means for forming said data-signal into sub-words, and causing each sub-word to be repeated a number of times, said redundancing means having

1. a first register;

2. means, associated with signals from said timing circuit for loading said data-signal into said first register;

3. an OR circuit;

4. means, associated with signals from said timing-circuit, for unloading the contents of said first register to said OR circuit, to cause a group of data-signals to form a sub-word of a frame;

5. a second register;

6. means, associated with signals from said timing-circuit, for shifting the data-signal at said OR circuit to said second register;

7. means, associated with signals from said timing-circuit, for unloading the contents of said second register to said OR circuit, to cause said group of data-signals to form a sub-word of another frame;

8. a third register;

9. means, associated with signals from said timing circuit, for shifting the data-signal at said OR circuit to said third register;

10. means, associated with signals from said timing circuit, for unloading the contents of said third register to said OR circuit to cause said group of data-signals to form a sub-word of still another frame -- whereby groups of data-signals are redundanced so that they form sub-words that appear in a plurality of frames;

E. means for producing a synchronizing-signal for a synchronizing-signal interval, having

1. generator means for producing a synchronizing-signal;

2. frame-counting means, associated with signals from said timing-circuit, for producing a first signal for the duration of said synchronizing-signal interval, and for producing a second signal at the termination of said synchronizing-signal interval;

F. means for combining the output of said synchronizing-signal producing means and the output of said redundancing means, comprising;

1. a synchronizing-signal gate-circuit;

2. a data-signal gate-circuit;

3. a combining OR circuit;

4. means for applying the synchronizing-signal to said synchronizing-signal gate-circuit;

5. means for applying the data-signal from the redundancing-means OR circuit to the data-signal gate-circuit;

6. means for applying said first signal from said frame-counting means to said synchronizing-signal gate-circuit, for enabling said synchronizing-signal gate-circuit, and for applying said synchronizing-signal to said combining OR circuit for the duration of said synchronizing-signal interval;

7. means for applying the first signal from said frame-counting means to said data-signal gate circuit, for disabling said data-signal gate circuit, and preventing application of said data-signal to said combining OR circuit for the duration of said synchronizing-signal interval;

8. means for applying said second signal from said frame-counting means to said synchronizing-signal gate circuit, and preventing application of said synchronization-signal to said combining OR circuit after the termination of said synchronizing-signal interval;

9. means for applying second signal from said frame counting means to said data-signal gate circuit, for enabling said data-signal gate, and applying said data-signal to said combining means OR circuit after the termination of said synchronizing-signal interval -- whereby said combining OR circuit receives, from the synchronizing-signal gate circuit, the synchronizing-signal for the duration of the synchronizing-signal interval, and then receives, from the data-signal gate circuit, the redundanced sub-words for the duration of the communication interval.

25. In a communication system wherein a plurality of receivers frequency-hop in individual frequency-hopping sequences, the individual frequency-hopping sequence of each individual receiver defining each individual receiver'"'"'s address, a transmitter comprising:

means for producing a frequency-hopping carrier-wave,

means for producing a data-signal;

redundancing means for forming said data-signal into sub-words, and repeating each sub-word a given number of times;

means for producing a synchronizing signal;

means for broadcasting said synchronizing-signal for a given synchronizing-signal interval; and

means for broadcasting said redundanced data-signal sub-words after termination of said synchronizing-signal interval.

27. means for applying said pseudo-random code from said code-generator to said matrix -- whereby the output from said matrix depends upon the input signal and upon the selected input-output path;

4. frequency-synthesizing means for producing frequencies that depend upon the input signals;

5. means for applying the output of said matrix to said frequency-synthesizer.

29. means for unloading the contents of said third register to said first OR circuit to combine said group of data-signals to form a sub-word of still another frame -- whereby groups of data-signals are redundanced so that they form sub-words that appear in a plurality of frames.

32. means for preventing application of said synchronizing-signal to said combining OR circuit after the termination of said synchronizing-signal interval;

9. means for enabling said data-signal gate, and applying said data-signal to said combining OR circuit after the termination of said synchronizing-signal interval -- whereby said combining OR circuit receives, from the synchronizing-signal gate-circuit, the synchronizing-signal for the duration of the synchronizing-signal interval, and then receives, from the data-signal gate circuit, the redundanced sub-words for the duration of the communication interval.

33. A transmitter comprising:

A. a timing-circuit having

1. master clock means for producing pulse-signals at a given frequency;

2. means for converting said pulse-signals to a desired clock frequency;

3. clock-pulse generator means, energized by said frequency-converted pulse-signals, for producing trigger-like clock-pulses at a clock-frequency, said clock pulses appearing on a common output;

4. timing generator means, energized by said clock-pulses, for producing timing-pulses, said timing-pulses appearing at individual outputs;

5. means for converting said pulse-signals to a modulating-signal;

B. a frequency hopping circuit having

1. code-generator means, energized by specific timing-signals, for producing a pseudo-random code;

2. a matrix, having selectable input-output paths;

3. means for applying said pseudo-random code from said code-generator to said matrix -- whereby the output from said matrix depends upon the input signal and upon the selected input-output path;

4. frequency-synthesizing means for producing frequencies that depend upon the input signals;

5. means for applying the output of said matrix to said frequency-synthesizer -- whereby the instantaneous output frequency of said frequency-synthesizer depends upon the instantaneous pseudo-random code and the selected input-output path of said matrix, and said frequency-synthesizer produces a carrier-wave having successive frames at different frequencies, a selected set of matrix input-output paths causing said frequency-synthesizer to produce an output that frequency-hops in the same sequence as an addressed station;

C. encoder means for converting input data to encoded data-signals;

D. redundancing means for forming data-signal into sub-words, and causing each sub-word to be repeated a number of times;

each repetition being in a different frame, said redundancing means having

1. a first register;

2. means, associated with signals from said timing circuit for loading said encoded data-signal into said first register;

40. The combination of claim 33, including

means in said receiver for producing signal-to-noise ratio signals for selected portions of said received redundanced data-signal;

and

means in said receiver for selecting optimal portions of said redundanced data-signal in accordance with said signal-to-noise ratio signals.

34. an OR circuit;

4. means, associated with signals from said timing-circuit, for unloading the contents of said first register to said OR circuit, to cause a group of encoded data-signals to form a sub-word of a frame;

5. a second register;

6. means, associated with signals from said timing-circuit, for shifting the data-signal at said OR circuit to said second register;

7. means, associated with signals from said timing-circuit, for unloading the contents of said second register to said OR circuit to cause said group of encoded data-signals to form a sub-word of another frame;

8. a third register;

9. means, associated with signals from said timing circuit, for shifting the data-signal at said OR circuit to said third register;

10. means, associated with signals from said timing circuit, for unloading the contents of said third register to said first OR circuit to cause said group of encoded data-signals to form a sub-word of still another frame -- whereby groups of encoded data-signals are redundanced so that they form sub-words that appear in a plurality of frames;

E. means for producing a synchronizing-signal for a synchronizing-signal interval, having

35. generator means for producing a synchronizing-signal having a start-code, an intermediate-code, and an end-code;

2. frame-counting means, associated with signals from said timing-circuit, for producing a first signal for the duration of said synchronizing-signal interval, and for producing a second signal at the termination of said synchronizing-signal interval;

F. means for combining the output of said synchronizing-signal producing means and the output of said redundancing means, comprising;

1. a synchronizing-signal gate circuit;

2. a data-signal gate circuit;

3. a combining OR circuit;

4. means for applying the synchronizing-signal to said synchronizing-signal gate circuit;

5. means for applying the data-signal from the redundancing-means OR circuit to the data-signal gate-circuit;

6. means for applying said first signal from said frame-counting means to said synchronizing-signal gate-circuit, for enabling said synchronizing-signal gate circuit, and for applying said synchronizing-signal to said combining OR circuit for the duration of said synchronizing-signal interval;

7. means for applying the first signal from said frame-counting means to said data-signal gate circuit, for disabling said data-signal gate-circuit, and preventing application of said data-signal to said combining OR circuit for the duration of said synchronizing-signal interval;

8. means for applying said second signal from said frame-counting means to said synchronizing-signal gate circuit, and preventing application of said synchronizing-signal to said combining OR circuit after the termination of said synchronizing-signal interval;

9. means for applying second signal from said frame-counting means to said data-signal gate circuit, for enabling said data-signal gate, and applying said data-signal to said combining OR circuit after the termination of said synchronizing-signal gate circuit, the synchronizing-signal for the duration of the synchronizing-signal interval, and then receives, from the data-signal gate circuit, the redundanced sub-words for the duration of the communication interval;

F. means for modulating the output of the combining OR circuit onto the frequency-hopping carrier-wave from the frequency-hopping circuit, having

1. a mixer;

2. means for applying the output of said combining OR circuit to said mixer, for producing a waveform having frequency-hopping frames -- during the synchronizing-signal interval said frames containing the synchronizing-signal, and after termination of said synchronizing-signal interval, said frames containing redundanced data sub-words;

G. means for transmitting the waveform produced by the modulating means.

36. For use with a frequency-hopping communication system wherein a transmitter may address a transmission to any selected receiver by (1) producing a carrier wave that frequency hops in the frequency-hopping sequence of the addressed receiver, (2) impressing a synchronizing-signal onto said addressed frequency-hopping carrier wave, and then (3) impressing a data-signal onto said addressed carrier wave, a receiver comprising:

A. means for producing a receiver-frequency that provides said receiver with a given frequency-hopping sequence, said given frequency-hopping sequence defining the address of said receiver, and producing a receiver-waveform;

B. means for varying said receiver-frequency in a search-pattern, resulting in reception of a transmission addressed to it, and further resulting in a received-waveform;

C. means for stabilizing said receiver-frequency to synchronize its operation to said received-waveform;

D. means for recovering the data in said received-waveform.

42. For use with a frequency-hopping communication system wherein a transmitter may address a transmission to any selected receiver by (1) producing a carrier wave that frequency hops in the frequency-hopping sequence of the addressed receiver, (2) impressing a synchronizing-signal onto said addressed frequency-hopping carrier wave, and then (3) impressing a data-signal onto said addressed carrier wave, a receiver comprising:

A. means for producing a receiver-frequency that provides said receiver with a given frequency-hopping sequence, said given frequency-hopping sequence defining the address of said receiver, and producing a receiver-waveform;

B. means for varying said receiver-frequency in a search-pattern, resulting in reception of a transmission addressed to it, and further resulting in a received-waveform;

C. means for stabilizing said receiver-frequency to synchronize its operation to said received-waveform;

D. means for recovering the data in said received-waveform;

limitation B comprising

means for determining the extent of coincidence between said receiver-waveform and said received-waveform;

means -- when said extent of coincidence is below a predetermined value -- for producing an unsatisfactory coarse-synchronization signal, and -- when said extent of coincidence is above said predetermined value -- for producing a satisfactory coarse-synchronization signal;

means, comprising said unsatisfactory coarse-synchronization signal, for varying said receiver-frequency to shift said receiver-waveform to produce a search mode of operation;

means, comprising said satisfactory coarse-synchronization signal modifying said receiver-frequency to terminate said search mode of operation.

49. The combination of claim 42, including

means, comprising a data-signal phase-comparator, for producing a data-signal phase indication;

means for applying said phase-corrected reference-waveform to said data-signal phase-comparator;

means for applying said given-waveform to said data-signal phase-comparator -- whereby the output of said data-signal phase-comparator is a signal that indicates the instantaneous phase of said bi-phase modulation relative to said phase-corrected reference waveform.

43. For use with a frequency-hopping communication system wherein a transmitter may address a transmission to any selected receiver by (1) producing a carrier wave that frequency hops in the frequency-hopping sequence of the addressed receiver, (2) impressing a synchronizing-signal onto said addressed frequency-hopping carrier wave, and then (3) impressing a data-signal onto said addressed carrier wave, a receiver comprising:

A. means for producing a receiver-frequency that provides said receiver with a given frequency-hopping sequence, said given frequency-hopping sequence defining the address of said receiver, and producing a receiver-waveform;

B. means for varying said receiver-frequency in a search-pattern, resulting in reception of a transmission addressed to it, and further resulting in a received-waveform;

C. means for stabilizing said receiver-frequency to synchronize its operation to said received-waveform;

D. means for recovering the data in said received-waveform;

limitation C including

means for time-wise comparison of the bit intervals of said receiver-waveform with the bit-intervals of said received-waveform;

means for producing a bit-synchronization error-signal in accordance with said comparison;

means, comprising said bit-synchronization error-signal, for varying said receiver-frequency to shift said receiver-waveform for producing a bit-synchronization mode of operation.

44. For use with a frequency-hopping communication system wherein a transmitter may address a transmission to any selected receiver by (1) producing a carrier wave that frequency hops in the frequency-hopping sequence of the addressed receiver, (2) impressing s synchronizing-signal onto said addressed frequency-hopping carrier wave, and then (3) impressing a data-signal onto said addressed carrier wave, a receiver comprising:

A. means for producing a receiver-frequency that provides said receiver with a given frequency-hopping sequence, said given frequency-hopping sequence defining the address of said receiver, and producing a receiver-waveform;

B. means for varying said receiver-frequency in a search-pattern, resulting in reception of a transmission addressed to it, and further resulting in a received-waveform;

C. means for stabilizing said receiver-frequency to synchronize its operation to said received-waveform;

D. means for recovering the data in said received-waveform;

limitation C including

means for time-wise comparison of said synchronizing-signal of said received-waveform with a corresponding synchronizing-signal in said receiver;

means for producing a word-synchronization error-signal in accordance with said comparison;

means, comprising said word-synchronization error-signal for varying said receiver-frequency to shift said receiver-waveform for producing a word synchronization mode of operation.

45. For use with a frequency-hopping communication system wherein a transmitter may address a transmission to any selected receiver by (1) producing a carrier wave that frequency hops in the frequency-hopping sequence of the addressed receiver, (2) impressing a synchronizing-signal onto said addressed frequency-hopping carrier wave, and then (3) impressing a data-signal onto said addressed carrier wave, a receiver comprising:

A. means for producing a receiver-frequency that provides said receiver with a given frequency-hopping sequence, said given frequency-hopping sequence defining the address of said receiver, and producing a receiver-waveform;

B. means for varying said receiver-frequency in a search-pattern, resulting in reception of a transmission addressed to it, and further resulting in a received waveform;

C. means for stabilizing said receiver-frequency to synchronize its operation to said received-waveform;

D. means for recovering the data received-waveform;

a code-generator;

a frequency-synthesizer;

means for applying the output of said code-generator to said frequency-synthesizer -- whereby the receiver produces said frequency-hopping receiver-waveform having said given frequency-hopping sequence;

means for determining the extent of coincidence between said receiver-waveform and said received-waveform;

means -- when said extent of coincidence is below a predetermined value -- for producing an unsatisfactory coarse-synchronization signal, and -- when said extent of coincidence is above said predetermined value -- for producing a satisfactory coarse-synchronization signal;

means, comprising said unsatisfactory coarse-synchronization signal, for varying said receiver-frequency to shift said receiver-waveform to produce a search mode of operation;

means for time-wise comparison of the bit-intervals of said receiver-waveform with the bit-intervals of said received-waveform;

means for producing a bit-synchronization error-signal in accordance with said comparison;

means, comprising said bit-synchronization error-signal for varying said receiver-frequency to shift and said receiver-waveform to produce a bit-synchronization mode of operation;

means for time-wise comparison of said synchronizing-signal of said received-waveform with a corresponding synchronizing-signal in said receiver;

means for producing a word-synchronization error-signal in accordance with said comparison;

means, comprising said word-synchronization error-signal for varying said receiver-frequency to shift said receiver-waveform to produce a word-synchronization mode of operation.

52. The combination of claim 45, wherein said code-generator comprises

a shift-signal terminal;

a plurality of binary stages;

a plurality of feedback connections interconnecting given said binary stages;

a pair of output terminals from each said binary-state;

whereby sequential shifting-signals applied to said shift-signal terminal cause said binary stages to assume particular sequential states controlled by the input signal and the feedback connections, the output signals from said binary stages forming the output code from said generator;

said matrix comprises

a plurality of input-output paths, said paths having

switch means for receiving a selected output from one of said binary-stage output-terminals;

a plurality of AND circuits, each adapted to produce an output signal upon the application of given input signals;

means for applying the output of said switches to said AND circuits;

whereby an instantaneous code and a given setting of said switches causes a given combination of said AND circuits to produce output signals -- a change in the instantaneous code, or a change of said switch settings causing a different combination of said AND circuits to produce output signals;

said frequency-synthesizer comprises

means for receiving synthesizer-input signals;

means for producing a plurality of frequencies;

means for causing synthesizer-input-signals to determine the frequency of the synthesizer-output signal;

means for applying the output of said AND circuits to said synthesizer input-signal-receiving means, and instantaneous code-signal and a given setting of said switches causing said frequency-synthesizer to produce an output of a given frequency, and a change of code-signal or a change of switch swttings causing said frequency-synthesizer to produce an output of a different frequency -- whereby a given sequence of code-signals and a given setting of said switches produces frequency-synthesizer output signals having a given frequency-hopping sequence, and the same sequence of code-signals and a different setting of said switches produces frequency-synthesizer output signals having a different frequency-hopping sequence.

47. A frequency-hopping circuit for producing a carrier-wave that hops from one frequency to another in a desired sequence, comprising:

A. a code-generator having

a shift-signal terminal;

a plurality of binary stages;

a plurality of feedback connections interconnecting given said binary stages;

a pair of output terminals from each said binary-state;

whereby sequential shifting-signals applied to said shift-signal terminal cause said binary stages to assume particular sequential states controlled by the input signal and the feedback connections, the output signals from said binary stages forming the output code from said generator;

B. a matrix having

a plurality of input terminals -- whereby said output code from said code-generator may be applied to said input terminals;

a plurality of input-output paths connected to said input terminals said paths having switch means for receiving an output from said binary -stage output-terminals;

a plurality of AND circuits, each adapted to produce an output signal upon the application of given input signals;

means for applying the output of said switches to said AND circuits -- whereby an instantaneous output code from said code-generator and a given setting of said switches causes a given combination of said AND circuits to produce output signals -- a change in the instantaneous code, or a change of said switch settings causing a different combination of said AND circuits to produce output signals;

C. a frequency-synthesizer comprising

means for receiving synthesizer-input signals;

means for producing a plurality of frequencies;

means for causing synthesizer-input-signals to determine the frequency of the synthesizer-output-signal;

D. means for applying the output of said AND circuits to said synthesizer input-signal-receiving means, an instantaneous code-signal and a given setting of said switches causing said frequency-synthesizer to produce an output of a given frequency, and a change of code-signal or a change of switch settings causing said frequency-synthesizer to produce an output of a different frequency -- whereby a given sequence of code-signals and a given setting of said switches produces frequency-synthesizer output signals having a given frequency-hopping sequency, and the same sequence of code-signals and a different setting of said switches produces frequency-synthesizer output signals having a different frequency-hopping sequence.

54. The combination of claim 47, including

means, comprising a data-signal phase-comparator, for producing a data-signal phase indication;

means for applying said phase-corrected reference waveform to said data-signal phase-comparator;

means for applying said given-waveform to said data-signal phase-comparator -- whereby the output of said data-signal phase-comparator is a signal that indicates the instantaneous phase of said bi-phase modulation relative to said phase-corrected reference waveform.

55. The combination of claim 47, wherein said data is available in a redundanced form and said data-recovery means comprises

means for obtaining each redundanced portion of said data;

means for obtaining the signal-to-noise ratio for each redundanced portion of said data;

means for utilizing the portion of said redundanced data having optimal signal-to-noise conditions.

48. In a system wherein an information signal appears as a bi-phase modulation on a given waveform of a given frequency, the combination comprising:

means for doubling the frequency of said given waveform;

means, comprising an oscillator, for producing a reference-waveform of the same frequency as said given waveform;

means for doubling the frequency of said reference-waveform;

means, comprising a mixer, for producing an error-signal corresponding to the phase-difference between said frequency-doubled given-waveform and said frequency-doubled reference-waveform;

means for applying said error-signal to said oscillator for phase correcting said reference waveform from said oscillator to have the same phase as said given waveform;

means, comprising an in-lock phase-comparator, for monitoring the phase-coincidence of said frequency-doubled given-waveforms and said frequency-doubled reference-waveform.

50. In a communication system wherein data is available in a redundanced form, a data-recovery circuit comprising:

means for obtaining each redundanced portion of said data;

means for obtaining the signal-to-noise ratio for each redundanced portion of said data;

means for utilizing the portion of said redundanced data having optimal signal-to-noise conditions.

51. In connection with a frequency-hopping communication system wherein a transmitter may address a transmission to any selected receiver by (1 ) producing a carrier wave that frequency hops in the frequency-hopping sequence of the addressed receiver, (2) impressing a synchronizing-signal onto said addressed frequency-hopping carrier wave, and then (3) impressing a data-signal onto said addressed carrier wave, a receiver comprising:

A. means for causing said receiver to have a given frequency-hopping sequence, said given frequency-hopping sequence defining the address of said receiver and producing a receiver-waveform, having

a code-generator;

a matrix having given input-output paths;

means for applying the output signal of said code-generator to said matrix -- whereby the output of said matrix depends upon said output signal from said code-generator and the input-output paths of said matrix;

a frequency-synthesizer;

means for applying the output of said matrix to said frequency synthesizer -- whereby the receiver produces said frequency-hopping receiver-waveform having said given frequency-hopping sequence;

timing-circuit means for producing trigger-pulses for triggering said code-generator;

means for applying said trigger-pulses to said code-generator;

means for causing said timing-circuit means to vary the rate at which said trigger pulses are applied to said code-generator -- whereby said receiver-waveform may be shifted;

B. means for causing said receiver to search for a transmission addressed to it, resulting in a received-waveform, having

means for determining the extent of coincidence between said receiver-waveform and the said received-waveform;

means -- when said extent of coincidence is below a predetermined value -- for producing an unsatisfactory coarse-synchronization signal, and -- when said extent of coincidence is above said predetermined value -- for producing a satisfactory coarse-synchronization signal;

means for causing said unsatisfactory coarse-synchronization signal to vary the frequency of said trigger-pulses applied to said code-generator for shifting said receiver-waveform to produce a search mode of operation;

C. means for causing said receiver to synchronize its operation to said received-waveform, having

means for time-wise comparison of the bit-intervals of said receiver-waveform with the bit-intervals of said received-waveform;

means for producing a bit-synchronization error-signal in accordance with said comparison;

means for causing said bit-synchronization error-signal to vary the frequency of said trigger-pulses applied to said code-generator to produce a bit-synchronization mode of operation;

means for time-wise comparison of said synchronizing-signal of said received-waveform with a corresponding synchronizing-signal in said receiver;

means for causing said word-synchronization error-signal to vary the frequency of said trigger pulses applied to said code-generator to produce a word-synchronization mode of operation.

56. Circuitry for redundancing data-signals, said redundancing means comprising:

means for dividing said data-signals into a plurality of individual sub-words; and

means for interlacing said individual sub-words into the live-portion of successive frames for providing said individual sub-words a plurality of times so that the data of said individual sub-words is available a plurality of times for redundancy.

57. Circuitry for redundancing data-signals, said redundancing means comprising:

means for dividing said data-signals into sub-words;

means for interlacing said sub-words into the live-portion of successive frames;

a plurality of registers;

means for storing one sub-word in one register;

means for transmitting said sub-word as a portion of one frame, and circulating said sub-word to a subsequent register; and

means for transmitting said sub-word from said subsequent register as a different portion of a subsequent frame.

58. Circuitry for redundancing data-signals, said redundancing means comprising:

means for dividing said data-signals into sub-words;

means for interlacing said sub-words into the live-portion of successive frames;

a first register;

means for loading said data-signal into said first register;

an OR circuit;

means for unloading the contents of said first register to said OR circuit, for multiplexing a group of data-signals to form a sub-word of a frame;

a second register;

means for shifting the data-signal at said first OR circuit to said second register;

means for unloading the contents of said second register to said first OR circuit for multiplexing said group of data-signals to form a sub-word of another frame;

a third register;

means for shifting the data-signal at said first OR circuit to said third register;

means for unloading the contents of said third register to said first OR circuit for multiplexing said group of data-signals to a sub-word of still another frame -- whereby groups of data-signals are redundanced so that they form sub-words that apppear in plurality of frames.

59. A frequency-hopping circuit for producing a carrier-wave that hops from one frequency to another in a desired sequence, comprising:

A. a code generator having

a shift-signal terminal;

a plurality of binary stages;

a plurality of feedback connections interconnecting given said binary stages;

a pair of output terminals from each said binary-state;

whereby, under the influence of sequential shifting-signals applied to said shift-signal terminal, said binary stages assume particular sequential states controlled by the input signal and the feedback connections, the output signals from said binary stages forming the output code from said generator;

B. an adjustable matrix having

a plurality of input terminals -- whereby said output code from said code-generator may be applied to said input terminals;

a plurality of input-output paths connected to said input terminals said paths having switch means for receiving an output from said binary-stage output-terminals;

a plurality of AND circuits, each adapted to produce an output signal upon the application of given input signals;

means for applying the output of said switches to said AND circuits -- whereby, under the influence of an instantaneous output code from said code-generator and a given setting of said switches, a given combination of AND circuits produces output signals -- a change in the instantaneous code, or a change of said switch settings providing a different combination of said AND circuits that produce output signals;

C. a frequency-synthesizer comprising

means for receiving synthesizer-input signals;

means for producing a plurality of frequencies;

means, comprising said synthesizer-input-signals, for energizing selected ones of the frequency-producers, to determine the frequency of the synthesizer-output-signal;

D. means for applying the output of said AND circuits to said synthesizer input-signal-receiving means, an instantaneous code-signal and a given setting of said switches energizing selected frequency-producers of said frequency-synthesizer to produce an output of a given frequency, and a change of code-signal or a change of switch settings energizing other frequency-producers of said frequency-synthesizer to produce an output of a different frequency -- whereby given sequence of code-signals and a given setting of said switches produces frequency-synthesizer output signals having a given frequency-hopping seqency, and the same sequence of code-signals and a different setting of said switches produces frequency-synthesizer output signals having a different frequency-hopping sequence.