Cryptography – Cryptanalysis
Patent
1988-11-07
1990-02-20
Cangialosi, Salvatore
Cryptography
Cryptanalysis
380 16, 455 1, H04N 7467, H07H 700
Patent
active
049032976
ABSTRACT:
A Television Signal Transmission Security System which provides a higher degree of security then previously possible by utilizing encoding and decoding technology which effectively prevents pirating by amateurs or experimenters. The television signal transmitted is encoded by injecting one or more modulated interfering signals in specific frequency slots in close proximity to the video carrier. Continuous or alternating interfering signals can be injected either above or below the video carrier between harmonics of the horizontal frequencies. Combinations of interfering signals provide coding techniques making the system virtually pirate proof. The interfering signal is removed by very narrow band rejection filters having a rejection band attenuation greater than about 40 dB over a bandwidth equal to the bandwidth between adjacent harmonics of the horizontal sweep frequency. The filters are constructed using advanced technology to produce the quartz crystal bulk resonators or surface acoustic wave filters. Pre-compensation at the transmitter improves overall amplitude and phase response to provide a nearly perfect decoded picture.
REFERENCES:
patent: 3202758 (1965-08-01), Browstein
patent: 4748667 (1988-05-01), Farmer et al.
patent: 4825467 (1989-04-01), Rist et al.
DeVries Adrian J.
Rist Bruno A.
Cangialosi Salvatore
International Telesystems, Inc.
O'Reilly David
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