Communication system

• US 4,245,346 A
• Filed: 02/07/1962
• Issued: 01/13/1981
• Est. Priority Date: 02/07/1962
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Magnavox Government and Industrial Electronics Company
• Inventors: Posthumus, Harry G., Grady, Robert J.
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US04/172,061
• Time in Patent Office: 6,915 Days
• Field of Search: 325/32, 325/33, 325/34, 325/35, 331/78, 178/22, 343/100.7, 343/6.8, 343/7.5, 343/6.8 R, 343/100 CL, 179/1.5, 455/26, 455/27, 455/28, 455/30
• US Class Current: 380/31
• CPC Class Codes: H04K 1/02 by adding a second signal to make the desired signal unintelligible

Abstract

1. In combination: a signal source for producing a signal having characteristic variations representative of intelligence, a first code source for producing a first code signal having apparently random characteristic variations but actually having characteristic variations conforming to a first particular code sequence which repeats after a relatively short time interval, a second code source for producing a second code signal likewise having apparently random characteristic variations but actually having characteristic variations conforming to a second particular code sequence which may repeat after a relatively long time interval, modifying circuit means responsive to the intelligence signal from the signal source and to a coded signal for modifying the characteristics of the coded signal in accordance with the characteristics of the intelligence signal, and means responsive to the signals from the first code source and to the signals from the second code source for initially introducing the first code signal to the modifying means for modification of such signal in accordance with the characteristics of the intelligence signal and of the first code signal and for subsequently introducing the second code signal to the modifying means for modification of the second code signal in accordance with the characteristics of the intelligence signal.

Claims

1. In combination:

a signal source for producing a signal having characteristic variations representative of intelligence, a first code source for producing a first code signal having apparently random characteristic variations but actually having characteristic variations conforming to a first particular code sequence which repeats after a relatively short time interval, a second code source for producing a second code signal likewise having apparently random characteristic variations but actually having characteristic variations conforming to a second particular code sequence which may repeat after a relatively long time interval, modifying circuit means responsive to the intelligence signal from the signal source and to a coded signal for modifying the characteristics of the coded signal in accordance with the characteristics of the intelligence signal, and means responsive to the signals from the first code source and to the signals from the second code source for initially introducing the first code signal to the modifying means for modification of such signal in accordance with the characteristics of the intelligence signal and of the first code signal and for subsequently introducing the second code signal to the modifying means for modification of the second code signal in accordance with the characteristics of the intelligence signal.

2. In combination:

a signal source for producing a signal representative of intelligence to be transmitted from one point to another point, a source for generating a carrier signal, means coupled to said signal source and to said generating source for modulating the carrier signal in accordance with the intelligence signal to produce a modulated intelligence signal, a first code source for producing a first code signal having pseudo-random characteristic variations which are repetitive after a particular relatively short time interval, a second code source for producing a second code signal having pseudo-random characteristic variations which are repetitive after a particular relatively long time interval, modifying circuit means responsive to the modulated intelligence signal and to a coded signal for modulating the coded signal in accordance with the characteristics of the modulated intelligence signal, and selecting means responsive to the signals from the first code source and the second code source for initially introducing the first code signal to the modifying means for modification of the first code signal in accordance with the characteristics of the modulated intelligence signal to produce a short-code coded intelligence signal and for subsequently introducing the second code signal to the modifying means for modification of the second code signal in accordance with the characteristics of the modulated intelligence signal to produce a long-code coded intelligence signal.

3. The combination defined in claim 2, including, an indicating signal source for producing an indicating signal, and means responsive to the short-code coded intelligence signal for causing the indicating signal to be transmitted from said one point to the other during the production of the short-code coded intelligence signal.

4. The combination defined in claim 2, including, an indicating signal source for producing an indicating signal, and means responsive to the short-code coded intelligence signal for causing such indicating signal to replace the intelligence signal and be transmitted from said one point to the other just prior to the production of the long-code coded intelligence signal.

5. In combination, a signal source for producing a signal representative of intelligence to be transmitted from one point to another, a source for producing a binary carrier signal having a first voltage state and a second voltage state, modulating means coupled to said sources and responsive to the intelligence signal and to the binary carrier signal for frequency modulating the carrier signal in accordance with the intelligence signal to produce a modulated intelligence signal having first and second voltage states and exhibiting transitions between such voltage states, a first code source for producing a first binary code signal having first and second voltage states and exhibiting transitions between such voltage states in conformance with an apparently random particular code sequence which is repetitive after a relatively short time interval, a second code source for producing a second binary code signal having first and second voltage states and exhibiting transitions between such voltage states in conformance with an apparently random particular code sequence but which may be repetitive after a relatively long time interval, inverting circuit means responsive to the modulated intelligence signal and to the first and second code signals for passing the code signals without any change in amplitude during the occurrence of the first voltage state in the modulated intelligence signal and for changing the amplitude of the code signals from the first voltage state to the second voltage state and from the second voltage state to the first voltage state during the occurrence of the second voltage state in the modulated intelligence signal, and means responsive to the first code signal and the second code signal for initially introducing the first code signal to the inverting circuit means for modification of the first code signal in accordance with the voltage characteristics of the modulated intelligence signal and for subsequently introducing the second code signal to the inverting circuit means for modification of the second code signal in accordance with the voltage characteristics of the modulated intelligence signal.

6. The combination defined in claim 5 and in which said intelligence signal has a particular identifying frequency during the introduction of the first code signal to the inverting circuit means.

7. The combination defined in clam 5 and in which said intelligence signal has a particular identifying frequency just prior to the introduction of the second code signal to the inverting circuit means.

8. In a coded communication system for operating upon a coded intelligence signal which is initially coded in accordance with a first code signal having apparently random characteristic variations but actually having characteristic variations conforming to a first particular code sequence having a repetitive pattern after a particular relatively short time interval and which is subsequently coded in accordance with a second code signal also having apparently random characteristic variations but actually having characteristic variations conforming to a second particular code sequence having a repetitive pattern after a particular relatively long time interval, a receiving station including:

means for receiving the coded intelligence signal, a code signal producing means for selectively producing signals corresponding to the first code signal and to the second code signal, decoding circuit means responsive to the signals from the receiving means and from the code signal producing means for detecting the coded intelligence signal to obtain the intelligence signal, and means coupled to the code signal producing means for initially obtaining the introduction of the first code signal from the code signal producing means to the decoding circuit means during the coding of the intelligence signal with the first code signal to obtain the detection of the intelligence signal by the decoding circuit means and for subsequently obtaining the introduction of the second code signal from the code signal producing means to the decoding circuit means during the coding of the intelligence signal with the second code signal to obtain the detection of the intelligence signal by the decoding circuit means.

9. The combination defined in claim 8, including, clock signal generating means coupled to the code signal producing means for controlling the clock frequency of the code signals produced by the code signal producing means.

10. In a coded communication system for operating upon a coded intelligence signal coded in accordance with a code signal having apparently random characteristic variations but actually having characteristic variations conforming to a particular code sequence having a particular clock frequency, a receiving station including:

means for receiving the coded intelligence signal, a decoding signal producing means for producing at least one decoding signal corresponding to the above mentioned code signal, decoding circuit means coupled to the receiving means for detecting the coded intelligence signal to obtain the intelligence signal, means coupled to the decoding signal producing means for obtaining the introduction of the decoding signal from the decoding signal producing means to the decoding circuit means to obtain the detection of the intelligence signal, clock signal generating means coupled to the decoding signal producing means for producing clock signals at an adjustable frequency and for introducing the clock signals to the decoding signal producing means to control the frequency at which the decoding signal is produced, control means coupled to the clock signal generating means for obtaining a particular change in the clock frequency from the particular value during a search interval to achieve correlation between the decoding signal produced by the decoding signal producing means and the coding of the received coded intelligence signal, and means coupled to the clock signal generating means and responsive to the decoding signals and to the coded intelligence signal for locking the clock signal generating means for the production of a particular frequency upon the achievement of correlation between the decoding signal produced by the decoding signal producing means and the coding of the received coded intelligence signal.

11. The combination defined in claim 10, including, signal correlation circuit means coupled to said receiving circuit means and to said decoding signal producing means for producing a control signal indicative of variations at the receiving means between the received coded intelligence signal and the decoding signal produced by said decoding signal producing means, and means coupled to the correlation circuit means and to the clock signal generating means for introducing said control signal to the clock signal generating means to control the frequency of the clock signals and to maintain correlation between the decoding signal produced by the decoding signal producing means and the coding of the received coded intelligence signal.

12. In a coded communication system for operating upon a coded intelligence signal which is initially coded in accordance with a first code signal having apparently random characteristic variations but actually having characteristic variations conforming to a first particular code sequence having a repetitive pattern after a particular relatively short time interval and which is subsequently coded in accordance with a second code signal also having apparently random characteristic variations but actually having characteristic variations conforming to a second particular coded sequence having a repetitive pattern after a particular relatively long time interval, a receiving station including:

means for receiving the coded intelligence signal, a decoding signal producing means for selectively producing first and second decoding signals respectively corresponding to the first code signal and to the second code signal, decoding circuit means responsive to the signals from the receiving means and from the coding signal producing means for detecting the coded intelligence signal to obtain the intelligence signal, control means coupled to the decoding signal producing means for initially obtaining the introduction of the first decoding signal from the decoding signal producing means to the decoding circuit means during the coding of the coded intelligence signal by the first coding signal to obtain the detection of the intelligence signal and for subsequently obtaining the introduction of the second decoding signal from the decoding signal producing means to the decoding circuit means during the coding of the intelligence signal by the second coding signal to obtain the detection of the intelligence signal, clock signal generating means coupled to the coding signal producting means for producing clock signals at an adjustable frequency and for introducing the clock signals to the decoding signal producing means to control the frequency of the decoding signals produced by the decoding signal producing means, and means coupled to the clock signal generating means for causing the clock frequency to shift from one value to another for a particular time interval until correlation is achieved with the received coded intelligence signal when such coded intelligence signal is coded in accordance with the first code signal and for causing the clock frequency to shift periodically between two values for a subsequent time interval until correlation is achieved with the received coded intelligence signal when said coded intelligence signal is coded in accordance with the second code signal.

13. In a coded communication system for operating upon a coded intelligence signal which is initially coded in accordance with a first code signal having apparently random characteristic variations but actually having characteristic variations conforming to a first particular code sequence having a repetitive pattern after a particular relatively short time interval and which is subsequently coded in accordance with a second code signal also having apparently random characteristic variations but actually having characteristic variations conforming to a second particular code sequence having a repetitive pattern after a relatively long time interval and which includes an indicating signal for indicating when the changeover from the initial coding to the subsequent coding is to occur, a receiving station including:

means for receiving the coded intelligence signal, a decoding signal producing means for selectively producing first and second decoding signals respectively corresponding to the first code signal and to the second code signal, decoding circuit means coupled to the receiving means and to the decoding signal producing means for detecting the coded intelligence signal to obtain the intelligence signal, control means coupled to the decoding signal producing means for initially obtaining the introduction of the first decoding signal from the decoding signal producing means to the decoding circuit means during the coding of the coded intelligence signal by the first code signal to obtain the intelligence signal and for subsequently obtaining the introduction of the decoding signal from the decoding signal producing means to the decoding circuit means during the coding of the coded intelligence signal by the second coding signal to obtain the intelligence signal, and means responsive to the indicating signal included in the coded intelligence signal for causing the control means to terminate the introduction of the first decoding signal to the decoding circuit means and to initiate the introduction of the second decoding signal to the decoding circuit means.

14. The combination defined in claim 13, including, clock signal generating means coupled to the decoding signal producing means for producing clock signals at an adjustable frequency and for introducing the clock signals to the decoding signal producing means to control the frequency of the first and second decoding signals produced by the decoding signal producing means, and means responsive to the indicating signal for causing the clock frequency to shift periodically between two values for a particular time interval after the introduction of the second code signal to the coded intelligence signal and until correlation is achieved between the second decoding signal and the coded intelligence signal.

15. In a coded communication system for operating upon a coded intelligence signal which is coded in accordance with a code signal having apparently random characteristic variations but actually having characteristic variations conforming to a particular code sequence having a particular clock frequency, a receiving station including:

means for receiving the coded intelligence signal, a decoding signal producing means for producing at least one decoding signal corresponding to the above mentioned code signal, decoding circuit means responsive to the signals from the receiving means and from the decoding signal producing means for detecting the coded intelligence signal to obtain the intelligence signal, means coupled to the decoding signal producing means for obtaining the introduction of the decoding signal from the decoding signal producing means to the decoding circuit means to obtain the intelligence signal, clock signal generating means coupled to the decoding signal producing means for producing clock signals at a frequency adjustable from a particular frequency and for introducing the clock signals to the decoding signal producing means to control the frequency of the decoding signal produced by the decoding signal producing means, first control means coupled to the clock signal generating means for obtaining particular variations in the clock frequency from the particular value during a search interval to achieve correlation between the decoding signal produced by the decoding signal producing means and the coding of the received coded intelligence signal, means operatively coupled to the clock signal generating means for locking the clock signal generating means at a particular frequency to maintain the correlation between the decoding signal and the coding of the received coded intelligence signal, and second control means coupled to the first control means to activate the first control means during periods of reception of the coded intelligence signal below an established threshold value.

16. The combination defined in claim 15, in which the second control means includes memory means for delaying the activation of the first control means by the second control means for a particular interval and for establishing the frequency of the clock signal generating means at a fixed value during each such particular interval.

17. In combination for use in each of a first station and a second station displaced from one another by a distance to be measured, a transmitting section including:

a first source for producing a signal to be transmitted, a second source for producing a code signal having a controllable clock frequency, transmitter control means coupled to the second source for controlling the clock frequency of the code signal produced thereby, and coding circuit means coupled to the first source and to the second source for producing a signal coded in accordance with a particular code sequence and which code sequence has a particular clock frequency established by the transmitter control means;

a receiving section for receiving the coded signal from the transmitting section of the other station and including means for receiving the coded signal, a decoding signal producing means for producing a signal corresponding to the code signal produced by the transmitting section of the other station, decoding circuit means coupled to the receiving means and to the decoding signal producing means and responsive to the decoding signal for decoding the received signal, receiver correlation means coupled to the receiving means and to the decoding signal producing means for producing a control signal indicative of the displacement of the received signal and the decoding signal, and receiver control means coupled to the correlation means and to the decoding signal producing means for controlling the clock frequency of the decoding signal in response to the correlation control signal from the correlation means to obtain a correlation between the received signal and the decoding signal;

first switching means coupled to said transmitting and receiving signals for causing the transmitting section of the first station to transmit the coded signal to the receiving section of the second station, second switching means coupled to said transmitting and receiving sections for subsequently causing the transmitted section of the second station to transmit the coded signal to the receiving section of the first station and to set the receiver control means at the first station to a condition such that said clock frequency is established at a particular displaced value; and

range indicating counter means coupled to the receiver correlation means of the first station and to the receiver control means of the first station to indicate the time required for correlation to be established between the signal received from the second station and the signal produced by the code signal producing means of the first station.

18. A system for measuring the range between a first station and a second station including:

means at the first station for transmitting a signal and for producing a particular code signal to code the transmitted signal, first means at the second station for receiving the coded signal from the first station and for producing a decoding signal corresponding to the particular code signal and displaced in phase with respect thereto by an amount corresponding to the range between the first and second station so as to decode the received coded signal, second means at the second station and coupled to the first means at the second station for transmitting a signal coded in accordance with the decoding signal produced at the second station, second means at the first station for receiving the coded signal from the second station and for producing the particular decoding signal to decode the received coded signal, control means at the first station and coupled to the second means at the first station for varying the particular decoding signal produced by the second means at the first station until correlation with the coded signal received from the second station is achieved, and range indicating means coupled to the last named control means for providing an indication as to the range between the first and second stations in accordance with the time required to achieve correlation between the decoding signal and the coded signal received from the second station.

19. A receiving station for use in a coded communication system for receiving a coded intelligence signal coded in accordance with a code signal, said receiving station including:

means for receiving the coded intelligence signal, decoding signal producing means for producing a first decoding signal having characteristics corresponding to the code signal and for producing a second decoding signal similar to the first decoding signal and time delayed with respect thereto, decoding circuit means responsive to the decoding signals produced by the decoding signal producing means for decoding the coded intelligence signal, detector means coupled to the decoding circuit means for respectively producing first and second control signals in response to the first and second decoding signals, and control means responsive to the first and second control signals produced by the detector means to control the producing means and maintain a synchronized condition between the decoding signals and the received coded intelligence signal.

20. In a coded communication system for operating upon a coded intelligence signal coded in accordance with a code signal having apparently random characteristic variations but actually having characteristic variations conforming to a particular code sequence having a particular clock frequency, a receiving station including:

means for receiving the coded intelligence signal, a decoding signal producing means for producing a first decoding signal and a signal decoding signal individually corresponding to the above mentioned code signal and displaced in time with respect to one another, decoding circuit means responsive to the first and second decoding signals produced by the decoding signal producing means for decoding the coded intelligence signal and for producing a first signal having a first particular frequency in response to the first decoding signal and a second signal having a second particular frequency in response to the second decoding signal, clock signal generating means coupled to the decoding signal producing means for controlling the clock frequency of the first and second decoding signals produced thereby, control means coupled to the decoding circuit means for selecting and comparing the first and second signals produced thereby to produce a control signal, and means coupled to the control means and to the clock signal producing means and responsive to the control signal from the control means for controlling the frequency of the clock signal generating means so as to maintain the first and second decoding signals synchronized with the received coded intelligence signal.

21. A system for producing a code signal having apparently random characteristic variations but actually having characteristic variations conforming to a particular code sequence which repeats after a relatively long time interval, said system including:

first code signal generating means for producing a first code signal having characteristic variations conforming to a first code sequence which repeats after a first particular time interval, second code generating means for producing a second code signal having characteristic variations conforming to a second code sequence which repeats after a second particular time interval different from the first particular time interval, and means coupled to the first code generating means and to the second code generating means for producing a third code signal having characteristic variations conforming to a code sequence which is repetitive only after a long interval as compared with the repetition intervals of the first and second code sequences and which is patterned in accordance with the repetition intervals of the first and second code sequences.

22. A system for producing a code signal having apparently random characteristic variations but actually having characteristic variations conforming to a particular code sequence which repeats after a relatively long time interval, said system including:

first shift register means for producing a first plurality of successive pulses individually occurring at apparently random times but conforming to a first code sequence which repeats after a first particular time interval, second circulating register means for producing a second plurality of successive pulses individually occurring at apparently random times but conforming to a second code sequence which repeats after a second particular time interval different from the first particular time interval, and mixing means coupled to the first circulating register means and to the second circulating register means for producing a code signal conforming to a code sequence which is repetitive only after a long interval as compared with the repetition intervals of the first and second code sequences and which is patterned in accordance with the repetition intervals of the first and second code sequences.

23. A system for producing a code signal having apparently random characteristic variations but actually having characteristic variations conforming to a particular code sequence which repeats after a relatively long time interval, said system including:

a first code selector for establishing a first particular code sequence, a first circulating register, means coupled to the first circulating register for introducing a pulse to the circulating register, means coupled to the first circulating register for sampling at successive intervals the introducing pulse during the circulation of the pulse through the first circulating register to produce a plurality of successive pulses in response thereto and for introducing the successive pulses to the first code selector to obtain a sereis of output pulses corresponding to said first particular code sequence, means coupled to the first code selector for introducing the serial output pulses therefrom to the first circulating register to be circulated therein and thereby forming a first code signal, a second code selector for establishing a second particular code sequence, a second circulating register, means coupled to the second circulating register for introducing a second pulse to the second circulating register, means coupled to the second circulating register for sampling the second pulse at successive intervals during the circulation of the second pulse through the second register and for introducing the successive pulses to the second code selector to obtain a series of output pulses corresponding to said second particular code sequence, and means responsive to the first and second code signals for producing a third code signal patterned in accordance with the sequences of the first and second code signals and having a code sequence which repeats only after a long interval as compared with the repetition intervals of the code sequences of the first and second code signals.

24. In combination at a first station for operating upon signals coded on a continuous basis in a particular asynchronous pseudo-random relationship with respect to time and continuously modulated by intelligence signals to obtain modulated intelligence signals and transmitted in a continuously modulated form from a second station, means at the first station for receiving the modulated intelligence signals from the second station, means at the first station for producing decoding signals continuously coded in the same particular asynchronous pseudo-random relationship with respect to time as the coded signals, synchronizing means at the first station and responsive to the decoding signals and to the modulated intelligence signals received at the first station for varying the times of occurrence of the decoding signals relative to the coding of the modulated intelligence signals during an asynchronous relationship between the decoding signals and the coding of the modulated intelligence signals and until the production of such a synchronous relationship, means at the first station and operatively coupled to the synchronizing means and to the decoding-signal-producing means for locking the operation of the decoding-signal-producing means to maintain the times of occurrence of the decoding signals upon the production of a synchronous relationship between the decoding signals and the modulated intelligence signals, means at the first station and responsive to the decoding signals and to the modulated intelligence signals for combining the signals to obtain the intelligence signals, and means operatively coupled to the synchronizing means and responsive to the decoding signals and to the modulated intelligence signals for obtaining an operation of the synchronizing means only upon each subsequent deviation of the decoding signals and the coding of the modulated intelligence signals from a sychronous relationship.

25. In combination at a first station for operating upon signals coded in a particular asychronous pseudo-random relationship with respect to time and modulated by intelligence signals to obtain modulated intelligence signals and transmitted in modulated form from a second station as the modulated intelligence signals, means at the first station for receiving the modulated intelligence signals from the second station, signal means at the first station for producing decoding signals in the particular asynchronous pseudo-random relationship with respect to time, means responsive to the decoding signals and to the modulated intelligence signals for varying the rate of occurrence of the decoding signals until the production of a particular relationship between the decoding signals and the occurrence of the coding in the modulated intelligence signal received at the first station, means operatively coupled to the synchronous means and the signal means for locking the signal means for the production of the decoding signals at a particular rate upon the occurrence of synchronization between the rate of occurrence of the decoding signals and the occurrence of the coding in the modulated intelligence signals, and means operatively coupled to the last mentioned means and responsive to the decoding signals and to the modulated intelligence signal received at the first station for combining these signals, only upon the occurrence of the particular relationship between the decoding signals and the coding of the modulated intelligence signals, to produce the intelligence signals.

26. In combination for use to provide for a transmission of intelligence from a first station to a second station removed from the first station, a signal source at the first station for producing a sequence of coding signals occurring in a particular asynchronous pseudo-random pattern, modulating means responsive to the sequence of coding signals from the signal source for modulating the coding signals in the sequence in accordance with the intelligence to produce modulated intelligence signals, means responsive to the modulated intelligence signals for obtaining a transmission of such signals to the second station, means at the second station for receiving the modulated intelligence signals transmitted from the first station, signal means at the second station for producing a sequence of decoding signals in a pattern corresponding to the pattern of the coding signals, synchronizing means at the second station and responsive to the received signals and to the decoding signals for varying the rate of occurrence of the decoding signals during a lack of a particular relationship between the decoding signals and the coding of the received signals until the production of the particular relationship between the decoding signals and the coding of the received signals, means operatively coupled to the synchronizing means and to the signal means for locking the signal means at a particular rate of occurrence corresponding to the production of the particular relationship between the decoding signals and the coding of the received signals, and means responsive to the received signals and to the decoding signals for detecting the received signals only upon the occurrence of the particular relationship between the decoding signals and the received signals, to produce the intelligence.

27. In combination for use at a first station to provide for a transmission of intelligence to a second station removed from the first station, a signal source at the first station for producing a sequence of coding signals occurring in a particular asynchronous pseudo-random pattern, modulating means responsive to the sequence of coding signals from the signal source for modulating the coding signals in the sequence in accordance with the intelligence to produce modulated intelligence signals, means responsive to the modulated intelligence signals for obtaining a transmission of such signals to the second station, means at the second station for receiving the modulated intelligence signals transmitted from the first station, signal means at the second station for producing a sequence of decoding signals in a pattern corresponding to the pattern of the coding signals, synchronizing means at the second station and responsive to the decoding signals and the received signals for initially obtaining a particular relationship between the occurrence of the decoding signals and the occurrence of the corresponding coding signals in the modulated intelligence signals received at the second station, means at the second station and responsive to the decoding signals and the received signals and operatively coupled to the synchronizing means for detecting the received signals in accordance with the decoding signals to obtain the intelligence only upon the occurrence of the particular relationship between the occurrence of the decoding signals and the occurrence of the corresponding coding signals in the modulated intelligence signals, means at the second station and operatively coupled to the decoding means and to the synchronizing means for locking the operation of the decoding means at a particular rate of occurrence of the decoding signals upon the occurrence of the particular relationship between the occurrence of the decoding signals and the occurrence of the corresponding coding signals in the modulated intelligence signals received at the second station, and means at the second station and responsive to the decoding signals and the received signals and operatively coupled to the synchronizing means for initiating an operation of the synchronizing means only upon each subsequent lack of the particular relationship between the occurrence of the decoding signals and the occurrence of the corresponding coding signals in the modulated intelligence signals to obtain such a synchronization.

28. In combination for use at a first station to provide for a transmission of intelligence to a second station removed from the first station, a first signal source at the first station for producing in a pseudo-random pattern a first sequence of signals having characteristics to promote a synchronization between the operation of the first and second stations, a second signal source at the first station for producing in a pseudo-random pattern a second sequence of signals different from the first sequence of signals and having characteristics for modulation by the intelligence means at the first station and responsive to the second sequence of signals and the intelligence for modulating the second sequence of signals by the intelligence to obtain the production of modulated intelligence signals, means at the first station and responsive to the signals in the first and second sequences for initially obtaining a transmission of the signals in the first sequence and then a transmission of the modulated intelligence signals in the second sequence, means at the second station for receiving the signals transmitted from the first station, means at the second station for producing decoding signals in the first and second sequences, means at the second station and responsive to the signals received at the second station in the second sequence and to the decoding signals in the second sequence to obtain a decoding of the intelligence transmitted from the first station in the modulated intelligence signals in accordance with a modulation of the modulated intelligence signals and the decoding signals and upon the production of a particular relationship between the received signals in the second sequence and the decoding signals in the second sequence;

and means at the second station and responsive to the signals received at the second station and operative during the reception of the signals in the first sequence to obtain a particular relationship between the signals produced by the decoding means in the first sequence and the reception of the signals in the first sequence from the first station and means at the second station and responsive to the production of the particular relationship between the signals received at the second station in the first sequence and the decoding signals in the first sequence for obtaining the production of the particular relationship between the signals received in the second sequence and the decoding signals in the second sequence.

29. In combination at a first station for operating upon signals coded in a particular asynchronous relationship with respect to time and modulated by intelligence signals to produce modulated intelligence signals and transmitted in a modulated form from a second station as the modulated intelligence signals, means at the first station for receiving the modulated intelligence signals from the second station, signal means at the first station for producing decoding signals having the same asynchronous pattern with respect to time as the coding signals, means at the first station and responsive to the modulated intelligence signals and to the decoding signals for varying in a particular time relationship the pattern of occurrence of the decoding signals with respect to the pattern of the coding of the modulated intelligence signals until a synchronous relationship between the occurrence of the coding signals and the pattern of the coding of the modulated intelligence signals, means operatively coupled to the synchronizing means and to the signal means for locking the signal means for the production of a particular asynchronous pattern upon the occurrence of the synchronous relationship between the occurrence of the coding signals and the pattern of the coding of the modulated intelligence signals received at the first station, means operatively coupled to the locking means and responsive to the decoding signals and to the modulated intelligence signals received at the first station for combining these signals to detect the intelligence signals upon the occurrence of the synchronous relationship between the occurrence of the coding signals and the pattern of the coding of the modulated intelligence signals received at the first station, and means responsive to a failure of reception of the modulated intelligence signals for maintaining the production of the decoding signals in the particular asynchronous pattern with respect to time and in a substantially constant timed relationship.

30. In combination at a first station for operating upon signals coded in a particular asynchronous relationship with respect to time and modulated by intelligence signals to provide modulated intelligence signals and transmitted in a modulated form from a second station as the modulated intelligence signals, means at the first station for receiving the modulated intelligence signals from the second station, signal means at the first station for producing decoding signals in the same particular asynchronous relationship with respect to time as the coded signals, synchronizing means at the first station and responsive to the decoding signals and the modulated intelligence signals received at the first station for varying the pattern of occurrence of the decoding signals with respect to the pattern of the coding of the modulated intelligence signals to obtain a particular relationship between the decoding signals and the coding of the modulated intelligence signals, means operatively coupled to the signal means and the synchronizing means for locking the operation of the signal means in a particular pattern upon the occurrence of the particular relationship between the decoding signals and the coding of the modulated intelligence signals, means operatively coupled to the locking means and responsive to the decoding signals and the modulated intelligence signals received at the first station for combining these signals to produce the intelligence signals upon the occurrrence of the particular relationship between the decoding signals and the coding of the modulated intelligence signals, and means responsive to the decoding signals and to the modulated intelligence signals and operatively coupled to the synchronizing means for placing the first station on a stand-by basis upon a failure to achieve the particular relationship between the occurrence of the decoding signals and the coding of the modulated intelligence signals within a particular period of time.

31. In combination at a first station for operating upon signals coded in a particular asynchronous relationship with respect to time and modulated by intelligence signals to provide modulated intelligence signals and transmitted in a modulated form from a second station as the modulated intelligence signals, means at the first station for receiving the modulated intelligence signals from the second station, signal means at the first station for producing decoding signals in the same particular asynchronous relationship with respect to time as the coded signals, synchronizing means at the first station and responsive to the decoding signals and to the modulated intelligence signals for varying the frequency of occurrence of the decoding signals until the production of a particular relationship between the decoding signals and the coding of the modulated intelligence signals received at the first station, means operatively coupled to the signal means and the synchronizing means for locking the operation of the signal means in a particular pattern upon the occurrence of the particular relationship between the decoding signals and the coding of the modulated intelligence signals, means operatively coupled to the locking means and responsive to the decoding signals and to the modulated intelligence signals for combining these signals to produce the intelligence signals upon the occurrence of the particular relationship between the decoding signals and the coding of the modulated intelligence signals received at the first station, means responsive to the modulated intelligence signals and operatively coupled to the locking means for maintaining the frequency of occurrence of the decoding signals for a particular period of time in the absence of reception of the modulated intelligence signals, and means operatively coupled to the locking means and responsive to the modulated intelligence signals for activating the synchronizing means upon a failure to receive the modulated intelligence signals for the particular period of time.

32. The combination set forth in claim 31 in which means are included for imposing a stand-by operation upon the receiving means upon a failure of the control means to obtain the particular relationship between the decoding signals and the coding of the modulated intelligence signals within a particular period of time after the activation of the synchronizing means.

33. In combination at a first station for operating upon signals coded in a particular asynchronous relationship with respect to time and received from a second station wherein the second station produces the coded signals in a relationship displaced from corresponding coding signals at the first station by a period of time corresponding to the distance between the stations, means at the first station for receiving the coded signals from the second station, means responsive to the coded signals received at the first station and responsive to the coded signals produced at the first station for varying in a particular pattern the frequency at which the coded signals are produced at the first station until the occurrence of a particular relationship between the coded signals received at the first station and the coded signals produced at the first station, and means responsive to the coded signals received at the first station and the coded signals produced at the first station to provide an indication as to the range between the first and second stations in accordance with the period of time required to produce the particular relationship between such signals.

34. In combination for operating upon signals coded in a first particular asynchronous relationship with respect to time and modulated by intelligence signals to provide modulated intelligence signals and transmitted in a modulated form from a first station to a second station as the modulated intelligence signals, means at the first station for providing signals coded in a second particular asynchronous relationship different from the first particular asynchronous relationship and coded to facilitate a synchronous relationship with the operation of the second station, means at the first station for providing a modifying signal, means at the first station and responsive to the signals coded in the second asynchronous relationship for obtaining a transmission only of such signals to the second station and for subsequently obtaining a transmission of the modifying signal to indicate that the modulated intelligence signals will follow and for thereafter obtaining a transmission of the coded signals in the first particular asynchronous relationship, means at the second station for receiving the coded signals, means at the second station for producing decoding signals initially coded in a pattern corresponding to the coded signals in the first and second particular asynchronous relationships, synchronizing means at the second station and responsive to the decoding signals and to the signals received at the second station for varying the frequency of occurrence of the decoding signals to obtain a particular relationship between the decoding signals and the coded signals received at the second station in the second particular asynchronous relationship and subsequently in the second particular relationship, means at the second station and operatively coupled to the synchronizing means and responsive to the modulated intelligence signals for detecting such signal upon the occurrence of the particular relationship between the decoding signals and the coded signals received at the second station in the second particular asynchronous relationship and subsequently in the first particular asynchronous relationship, and means at the second station and responsive to the modifying signal received from the first station for activating the last mentioned detecting means to obtain a detection of the modulated intelligence signals upon the occurrence of the particular relationship between the decoding signals and the coded signals received at the particular station in the first particular asynchronous relationship.

35. In combination at a first station for operating upon signals coded in a particular asynchronous relationship with respect to time and modulated by intelligence signals and transmitted in a modulated form from a second station, means at the first station for receiving the modulated intelligence signals from the second station, and means at the first station and operatively coupled to the synchronizing means and responsive to the production of the particular relationship between the decoding signals and the coding of the modulated intelligence signals for locking the operation of the clock means to maintain the production of the clock signals at a frequency to maintain the production of such particular relationship, means at the first station for producing decoding signals in the same particular asynchronous relationship as the coded signals, clock means at the first station for producing clock signals on a periodically recurrent basis, means at the first station and responsive to the clock signals for synchronizing the occurrence of the decoding signals with the frequency of the clock signals, means at the first station and responsive to the decoding signals and to the modulated intelligence signals received at the first station for detecting the modulated intelligence signals to produce the intelligence signals, synchronizing means at the first station and responsive to the decoding signals and the modulated intelligence signals for varying the frequency of the clock signals to maintain a particular relationship between the decoding signals and the coding of the modulated intelligence signals.

36. In combination at a first station for operating upon signals coded in a particular asynchronous relationship with respect to time and modulated by intelligence signals to provide modulated intelligence signals and transmitted in a modulated form from a second station as the modulated intelligence signals, means at the first station for receiving the modulated intelligence signals from the second station, means at the first station for producing decoding signals in the same particular asynchronous relationship as the coded signals, clock means for producing clock signals on a recurrent basis, means at the first station and responsive to the clock signals for synchronizing the production of the decoding signals with the frequency of occurrence of the clock signals, synchronizing means at the first station and responsive to the decoding signals and the modulated intelligence signals and operatively coupled to the clock means for varying the frequency of the clock signals in a particular pattern until the production of a particular relationship between the decoding signals and the coding of the modulated intelligence signals, means at the first station and operatively coupled to the clock means for locking the operation of the clock means at a particular frequency for maintaining the particular relationship between the decoding signals and the coding of the modulated intelligence signals upon the production of such particular relationship and means at the first station and responsive to the decoding signals and the modulated intelligence signals and operatively coupled to the last mentioned means for detecting the modulated intelligence signals only upon the occurrence of the particular relationship between the decoding signals to obtain the intelligence, and the coding of the modulated intelligence signals.

37. In combination at a first station for operating upon signals coded in a particular asynchronous relationship with respect to time and modulated by intelligence signals to provide modulated intelligence signals and transmitted in modulated form from a second station as the modulated intelligence signals, means at the first station for receiving the modulated intelligence signals from the second station, means at the first station for producing first decoding signals in the same particular asynchronous relationship as the coded signals, means at the first station and responsive to the first decoding signals for producing second decoding signals in the same particular asynchronous relationship as the coded signals and on a delayed basis with respect to the first decoding signals, means at the first station and responsive to the first and second decoding signals and to the modulated intelligence signals for producing control signals representing phase displacements from a particular phase relationship between the modulated intelligence signals and the first and second decoding signals, means at the first station and responsive to the control signals produced by the last mentioned means to vary the times of occurrence of the first and second decoding signals in accordance with the characteristics of the control signal for the production of a particular relationship between the first decoding signals and the coding of the modulated intelligence signals, and means at the first station and responsive to the modulated intelligence signals and the first decoding signals and operatively coupled to the last mentioned means for detecting the modulated intelligence signals, upon the production of the particular relationship between the first decoding signals and the coding of the modulated intelligence signals, to produce the intelligence signals.

38. In combination at a first station for operating upon signals coded in a particular asynchronous relationship with respect to time and modulated by intelligence signals to provide modulated intelligence signals and transmitted in modulated form from a second station as the modulated intelligence signals, means at the first station for receiving the modulated intelligence signals from the second station, means at the first station for producing first decoding signals in the same particular asynchronous relationship as the coded signals, means at the first station and responsive to the first decoding signals for producing second decoding signals having the same particular asynchronous relationship as the coded signals and having a particular phase displacement from the first decoding signals, means at the first station for producing clock signals on a recurrent basis, means at the first station and responsive to the clock signals for obtaining the production of the first and second decoding signals in accordance with the frequency of the clock signals, means at the first station and responsive to the first and second decoding signals and to the modulated intelligence signals for producing control signals in accordance with the relative phase between the first decoding signals and the coding of the modulated intelligence signals and between the second decoding signals and the coding of the modulated intelligence signals, means at the first station and responsive to the control signals produced by the last mentioned means for varying the frequency of the clock signals to obtain a particular relationship between the first decoding signals and the coding of the modulated intelligence signals, and means at the first station and responsive to the first decoding signals and the modulated intelligence signals for combining these signals to obtain the intelligence signals.

39. In combination for use to provide for a transmission of intelligence from a first station to a second station removed from the first station, a signal source at the first station for producing a sequence of coding signals occurring in a particular asynchronous pseudo-random pattern, modulating means at the first station and responsive to the sequence of coding signals from the signal source for modulating the signals in the sequence in accordance with the intelligence to produce modulated intelligence signals, means at the first station and responsive to the modulated intelligence signals for obtaining a transmission of such signals to the second station, means at the second station for receiving the modulated intelligence signals transmitted from the first station, signal means at the second station for producing decoding signals in the same asynchronous pattern as the coding of the modulated intelligence signals at the first station, synchronizing means at the second station and responsive to the decoding signals and to the modulated intelligence signals received at the second station for varying the times of occurrence of the decoding signals to provide a particular relationship between the decoding signals and the coding of the modulated intelligence signals, locking means operatively coupled to the signal means and responsive to the production of the particular relationship between the decoding signals and the coding of the modulated intelligence signals for locking the operation of the signal means to maintain such particular relationship, and means at the second station and responsive to the decoding signals and to the modulated intelligence signals for combining these signals, upon the production of the particular relationship between the decoding signals and the modulated intelligence signals, to produce the intelligence signals.

40. In combination for use to provide for a transmission of intelligence from a first station to a second station removed from the first station, a signal source at the first station for producing a sequence of coding signals occurring in a particular asynchronous pseudo-random pattern, means at the first station and responsive to the coding signals and to the intelligence for modulating the coding signals in accordance with the intelligence to produce modulated intelligence signals, means at the first station and responsive to the modulated intelligence signals for transmitting the signals to the second station, means at the second station for receiving the modulated intelligence signals, clock means at the second station for producing clock signals on a recurrent basis, means at the second station and responsive to the clock signals for producing decoding signals at a rate related to the frequency of the clock signals and in a pattern corresponding to the asynchronous pattern of the coding signals, synchronizing means at the second station and responsive to the decoding signals and to the coding of the modulated intelligence signals for varying the frequency of the clock signals to maintain a particular relationship between the decoding signals and the coding of the modulated intelligence signals, means at the second station and responsive to the production of the particular relationship between the decoding signals and the coding of the modulated intelligence signals for locking the operation of the clock means to maintain the production of the clock signals as a rate for maintaining such particular relationship, and means at the second station and responsive to the decoding signals and to the modulated intelligence signals and operative upon the production of the particular relationship between the decoding signals and the coding of the modulated intelligence signals for detecting the intelligence.

41. In combination to provide for a transmission of intelligence from a first station to a second station removed from the first station, a signal source at the first station for producing a sequence of coding signals occurring in a particular asynchronous pattern, means at the first station and responsive to the coding signals and to the intelligence for modulating the coding signals in accordance with the intelligence to produce modulated intelligence signals, means at the first station and responsive to the modulated intelligence signals for transmitting the signals to the second station, means at the second station for receiving the modulated intelligence signals transmitted from the first station, means at the second station for producing first decoding signals in the particular asynchronous pattern, means at the second station and responsive to the first decoding signals for producing second decoding signals having a particular phase relationship to the first decoding signals, means responsive to the first and second decoding signals and to the modulated intelligence signals for varying the times of occurrence of the first and second decoding signals to maintain particular phase relationships between the first decoding signals and the coding of the modulated intelligence signals and between the second decoding signals and the coding of the modulated intelligence signals, and means responsive to the first decoding signals and the modulated intelligence signals for detecting the modulated intelligence signals to produce the intelligence.

42. In combination for use at a first station to provide for a transmission of intelligence from the first station to a second station removed from the first station;

first means for providing a relatively short sequence of first signals in a pseudo-random code for a particular period of time to obtain a synchronization in the operation of the first and second stations,

second means operatively coupled to the first means for providing for the transmission of a second signal during the transmission of the first signal to provide an indication to the second station that the first signals do not represent intelligence,

third means operatively coupled to the first means for providing a relatively long sequence of third signals in a pseudo-random code after the production of the first signals,

fourth means operatively coupled to the third means for modulating the third signals in accordance with the intelligence to provide modulated intelligence signals, and

fifth means operatively coupled to the fourth means for obtaining a transmission of the modulated intelligence signals to the second station.

43. In combination for use at a first station to provide for a transmission of intelligence from the first station to a second station removed from the first station;

a signal source for providing a sequence of coding signals,

first control means operatively coupled to the signal source for obtaining the production of first signals by the source in a first asynchronous sequence for a first particular period of time to provide for a synchronization in the operation of the first and second stations;

second control means operatively coupled to the first control means for obtaining a transmission of a second signal during the transmission of the first signals to indicate that the first signals do not represent intelligence,

third control means operatively coupled to the first control means and the signal source for obtaining the production of third signals by the source in a second asynchronous sequence different from the first asynchronous sequence and for obtaining the production of the third signals after the production of the first signals, and

means operatively coupled to the third control means for modulating the third signals with the intelligence to obtain modulated intelligence signals.

44. In combination for use at a first station to provide for a transmission of intelligence from the first station to a second station removed from the first station;

first means for providing clock signals at a particular frequency,

second means operatively coupled to the first means for providing a relatively short sequence of first encoding signals in a pseudo-random code for a particular period of time in synchronism with the clock signals to obtain a synchronization in the operation of the first and second stations,

third means operatively coupled to the second means for providing for the transmission of a second signal with particular characteristics during the transmission of the first signal to provide an indication to the second station that the first signals do not represent intelligence,

fourth means operatively coupled to the first and second means for providing a relatively long sequence of second encoding pulses in a pseudo-random code in synchronism with the clock signals and after the production of the first encoding signals, and

fifth means operatively coupled to the first and fourth means for modulating the second encoding signals in synchronism with the clock signals to provide modulated intelligence signals.

45. The combination set forth in claim 44, including,

sixth means operatively coupled to the fifth means for obtaining a transmission of the modulated intelligence signals.