US3696207A
Expired / Lapsed
US
⏱️ 0.0 years remaining
System for the transmission of intelligence by means of scrambled audiosignals
Assignee: US Philips Corp
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Filing: 1970-05-05
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Granted: 1972-10-03
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Expires: 1990-05-05
Abstract
Abstract A system for the transmission of intelligence signals by means of scrambled audio signals comprising a transmitter, that employs the frequency shift generator to also produce a control signal that is added to the scrambled audio signals to be transmitted to the receiver. The receiver separates the control signal from the scrambled audio signals and employs this control signal to synchronize the receiver with the transmitter thereby effecting the demodulation of the scrambled audio signals by the receiver.
Inventors
- 👤 Seth Johan Ronald Lundin
- 👤 Bengt Harry Bjorkman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:01
CPC Classifications
H; H04; H04K; H04K1/00; H04K1/003
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
276 words
A system for the transmission of intelligence signals by means of scrambled audiosignals, comprising a transmitter and a receiver, said transmitter comprising signal input means for said intelligence signals, a source of auxiliary information signals having a periodic pulse pattern not correlated with said intelligence signals, said source comprising an oscillator, a feedback connected shift register coupled to said oscillator to produce a predetermined frequency variation by varying the frequency of said oscillator, and a frequency shift generator coupled to control said shift register and provide a control signal at a frequency within the frequency band of said intelligence signals and a phase representing the shift pulses produced by said shift pulse generator, means for combining said intelligence signals and said auxiliary information signals to produce a scrambled audiosignal, means for adding said control signal to said scrambled audiosignals for transmission to said receiver, said receiver comprising signal input means for receiving said scrambled audiosignals with said control signal, means for separating said scrambled audiosignals from said control signal, a source of auxiliary information signals having a periodic pulse pattern identical to the periodic pulse pattern of said transmitter, said source comprising an oscillator, a shift register coupled to said oscillator to produce a predetermined frequency variation by varying the frequency of said oscillator, and a frequency shift generator coupled to control said shift register, means for applying said control signal to said frequency shift generator to control said generator to establish phase coincidence between the output signal of said generator and said control signal, and means for combining said source of auxiliary information signals with said scrambled audiosignal to effect demodulation of said intelligence signals.
Claim 2
Independent Claim
276 words
A system for the transmission of intelligence signals by means of scrambled audiosignals, comprising a transmitter and a receiver, said transmitter comprising signal input means for said intelligence signals, a source of auxiliary information signals having a periodic pulse pattern not correlated with said intelligence signals, said source comprising an oscillator, a feedback connected shift register coupled to said oscillator to produce a predetermined frequency variation by varying the frequency of said oscillator, and a frequency shift generator coupled to control said shift register and provide a control signal at a frequency within the frequency band of said intelligence signals and a phase representing the shift pulses produced by said shift pulse generator, means for combining said intelligence signals and said auxiliary information signals to produce a scrambled audiosignal, means for adding said control signal to said scrambled audiosignals for transmission to said receiver, said receiver comprising signal input means for receiving said scrambled audiosignals with said control signal, means for separating said scrambled audiosignals from said control signal, a source of auxiliary information signals having a periodic pulse pattern identical to the periodic pulse pattern of said transmitter, said source comprising an oscillator, a shift register coupled to said oscillator to produce a predetermined frequency variation by varying the frequency of said oscillator, and a frequency shift generator coupled to control said shift register, means for applying said control signal to said frequency shift generator to control said generator to establish phase coincidence between the output signal of said generator and said control signal, and means for combining said source of auxiliary information signals with said scrambled audiosignal to effect demodulation of said intelligence signals.
Claim 3
Dependent Claim
63 words
A transmission system as claimed in claim 1 wherein the frequency shift generator of said receiver further comprises a closed loop comprising a phase detector for receiving said control signal and the output of saId frequency shift generator to control said frequency shift generator thereby maintaining a predetermined mutual phase position between said control signal and the output of said frequency shift generator.
Claim 4
Dependent Claim
35 words
A system as claimed in claim 1 wherein said control signal is formed by the difference signal obtained by comparison of two signals having a difference frequency within the frequency band of the intelligence signal.
Claim 5
Dependent Claim
198 words
A system as claimed in claim 1 wherein synchronizing transmitter is provided with means for synchronizing the shift registers controlled by the shift registers for generating and transmitting to the receiver during at least one interval at the beginning of said intelligence signal transmission, pulses having a frequency within the transmitted frequency band, said pulses being synchronized in time with the shift register in said transmitter so that it appears at a predetermined condition of said register, and the receiver is provided with means for receiving said synchronizing pulse to ensure the corresponding setting of the shift register of the receiver in the period of time determined by the pulse thereby syncrhonizing the periodic pulse pattern of said receiver with the periodic pulse pattern of the transmitter. trailing 5. A system as claimed in claim 4 wherein the trailng edge of said synchronizing pulses define the period of time when the predetermined condition in the shift register of the transmitter occurs, and means in the receiver sensitive to said synchronization pulses to set and maintain the shift register in a predetermined condition during the occurrence of said synchronizing pulses and release the register when said synchronizing pulses terminate.
Claim 6
Dependent Claim
55 words
A transmission system as claimed in claim 1 wherein the signal input of said transmitter further comprises a filter functioning as a low pass filter, said filter acting as a clamping network for mainly the higher frequencies of said intelligence signals, the cut-off frequency of said filter being within the frequency band to be transmitted.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-03 | 1976-04-03 | 1976-10-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-03 | 1980-04-03 | 1980-10-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-03 | 1984-04-03 | 1984-10-03 | $7700.00 | Window Closed / Lapsed |