Digitally-controlled analog encrypton

Details Digitally-controlled analog encrypton Digitally-controlled analog encrypton

1980-09-29

1983-06-21

Buczinski, S. C.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358 21V, 358 34, 358121, 179 15FS, H04N 716

Patent

active

043896715

ABSTRACT:
An apparatus for scrambling a television signal in which horizontal lines of the transmitted television picture are selectively inverted in accordance with the state of a pseudorandom noise generator. In order to permit correction of the throughput gain as well as the throughput offset at the receiving end of the communication link so as to obtain a desired level of picture quality, particularly in a satellite communication system, an analog calibration signal representing both black and white levels is inserted into a horizontal line of the vertical retrace interval at the transmission end of the link. This calibration signal is then detected at the receiving end of the link and the signal levels are adjusted as needed. In addition, a randomly-varying key code signal for resetting the pseudorandom noise generator is randomly inserted into another horizontal line of the vertical retrace period to control scrambling. The audio portion of the television signal is also scrambled by randomly shifting the audio carrier between first and second offset frequencies.

REFERENCES:
patent: 2402058 (1946-06-01), Loughren
patent: 2872507 (1959-02-01), Druz
patent: 3054857 (1962-09-01), Weiss
patent: 3124748 (1964-03-01), Webb, Jr.
patent: 3440338 (1969-04-01), Walker
patent: 3679816 (1972-07-01), Avins et al.
patent: 3919462 (1975-11-01), Hartung et al.
patent: 4058677 (1977-11-01), Maitland et al.
patent: 4075660 (1978-02-01), Horowitz

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