Sound masking in phase reversal TV scrambling system

Details Sound masking in phase reversal TV scrambling system Sound masking in phase reversal TV scrambling system

1987-02-26

1989-01-31

Cangialosi, Salvatore

Cryptography

Cryptanalysis

380 12, 380 17, G06K 102

Patent

active

048022136

ABSTRACT:
A TV scrambling system includes means for scrambling a TV signal by phase reversing the carrier at a horizontal rate. A sound masking circuit includes a phase locked loop which operates at five times the horizontal frequency. The program sound signal is used to frequency modulate the VCO in the phase locked loop and the output is added to the regular program sound for modulation onto an RF carrier to create an interfering sound signal. Detection of the program sound signal in an unauthorized receiver is accompanied by beating between the 5 H harmonic of the phase reversal frequency and the interfering sound signal, which masks the program sound.

REFERENCES:
patent: 3347982 (1967-10-01), Bass et al.
patent: 4074311 (1978-02-01), Tanner et al.
patent: 4099203 (1978-07-01), Garodnick et al.
patent: 4148064 (1979-04-01), Reed
patent: 4467353 (1984-08-01), Citta et al.
patent: 4706283 (1987-11-01), Citta et al.
patent: 4706284 (1987-11-01), Citta et al.

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