04389671 is referenced by 190 patents and cites 9 patents.

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.

Title
Digitally-controlled analog encrypton
Application Number
6/191844
Publication Number
4389671
Application Date
September 29, 1980
Publication Date
June 21, 1983
Inventor
David K Campbell
Melbourne Beach
FL, US
Charles R Burr Jr
Palm Bay
FL, US
Ronald S Posner
Indian Harbor Beach
FL, US
Agent
Antonelli Terry & Wands
Assignee
Harris Corporation
FL, US
IPC
H04N 7/16
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