CATV system transmitting a scrambled television signal

Details CATV system transmitting a scrambled television signal CATV system transmitting a scrambled television signal

1989-12-11

1990-08-28

Tarcza, Thomas H.

Cryptography

Key management

Having particular key generator

380 19, 380 20, H04K 100

Patent

active

049532081

ABSTRACT:
A method of scrambling a television signal is provided in which, during a horizontal blanking interval and during a vertical blanking interval, a video signal is compressed and a key signal containing information concerning the compression is superimposed on an audio signal in the horizontal blanking period. The method is characterized by superimposing a pseudo-key signal on an audio signal in the vertical blanking interval, making the key signal contain information concerning the position of a vertical blanking interval, and fixing a video signal in a predetermined number of horizontal scanning periods before a vertical synchronizing signal portion in the vertical blanking interval at a constant level while eliminating color bursts in a predetermined number of horizontal scanning periods before and after the vertical synchronizing signal portion in the vertical blanking interval. In this way, unauthorized users are prohibited from receiving the signal, and unauthorized access is made difficult.

REFERENCES:
patent: 3801732 (1974-04-01), Reeves
patent: 4064536 (1977-12-01), Saeki et al.
patent: 4338628 (1982-07-01), Payne et al.
patent: 4353088 (1982-10-01), dea Toonder et al.
patent: 4571615 (1986-02-01), Robbins et al.
patent: 4691354 (1987-09-01), Palminteri
patent: 4794643 (1988-12-01), Saeki et al.
patent: 4839922 (1989-06-01), Imasaki et al.

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