Cryptography – Key management – Having particular key generator
Patent
1990-12-20
1992-08-04
Tarcza, Thomas H.
Cryptography
Key management
Having particular key generator
380 10, H04N 7167
Patent
active
051366410
ABSTRACT:
A scrambled video digital transmission link comprising an amplitude modulator, a scrambler, an amplitude demodulator and frequency conversion apparatus for providing a scrambled video signal in a baseband format and a modified sound signal which includes video sync information which is used to restore the video signal for use in a subscriber's television set. The scrambled video signal in the baseband format and the modified sound signal are converted to a digital signal before transmission by a laser driven fiber optic transmission line to a hub station. In the hub station there is provided digital-to-analog signal converting apparatus, amplitude modulating apparatus and frequency conversion apparatus for recreating the scrambled video signal and modified sound signal generated in the head end station. The signals transmitted between the transmitter and the receiver may be in a digital pulse code modulation (PCM) format or in a format produced by digital modulation of an r.f. carrier, such as quarternary phase shift keying (QPSK) techniques.
REFERENCES:
patent: 4623920 (1986-11-01), Defresne et al.
patent: 4688246 (1987-08-01), Eilers et al.
patent: 4688249 (1987-08-01), Hayes et al.
patent: 5040211 (1991-08-01), Schrieber
Cain David
Synchronous Communications, Inc.
Tarcza Thomas H.
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