Cryptography – Key management – Having particular key generator
Patent
1990-03-30
1991-11-05
Gregory, Bernarr E.
Cryptography
Key management
Having particular key generator
380 19, H04N 7167
Patent
active
050635948
ABSTRACT:
A system for level-compressing a sync signal component of a video intermediate frequency signal to scramble the signal. A compression pulse generation circuit generates a compression pulse in synchronism with a sync signal. A level compression circuit level compresses the sync signal component of the video intermediate frequency signal in response to the compression pulse. A sine wave generation circuit generates a sine wave having a frequency n times that of the sync signal in synchronism with the sync signal. A control data generation circuit generates control data for controlling a phase of the sine wave and generates a sine wave phase-controlled in accordance with the control data. A superposing circuit superposes the phase-controlled sine wave on an audio intermediate frequency signal and outputs a superposed signal. An output circuit outputs the level-compressed signal and the audio intermediate frequency signal. A detector detects the superposed signal and extracts the sine wave. A compression position detector detects a compression position and outputs a detection signal. An expansion pulse generation circuit generates an expansion pulse on the basis of the sine wave and the detection signal. A level expansion circuit expands the sync signal component in response to the expansion pulse.
REFERENCES:
patent: 4839922 (1989-06-01), Imasaki et al.
patent: 4901351 (1990-02-01), Tanaka et al.
Gregory Bernarr E.
Kabushiki Kaisha Toshiba
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