Information security system

Details Information security system Information security system

1983-02-14

1986-04-08

Buczinski, S. C.

Telecommunications

Carrier wave repeater or relay system

Frequency or phase modulation

179 15FS, 358114, 358121, H04K 100

Patent

active

045817650

ABSTRACT:
A system is disclosed for encoding and decoding the audio signal portion of a television signal to prevent unauthorized reception of the audio signal. At the encoding stage, the audio signal is applied to a multiplier which combines the audio signal with a programmable carrier having a frequency controlled by a frequency selection protocol to produce an output signal which is spectrally inverted from the original audio signal. The spectrally inverted signal from the multiplier is applied to a sideband filter which filters out the upper sideband of the spectrally inverted signal to produce an encoded signal having the same bandwidth as that of the original audio signal. At the decoding stage, the carrier signal is phase-shifted to compensate for phase delay imparted to the encoded signal in the encoding process and combined with the encoded signal to decode the encoded signal.

REFERENCES:
patent: 2509716 (1950-05-01), Aubert
patent: 3824468 (1974-07-01), Zegers et al.
patent: 4216500 (1980-08-01), St. Louis
patent: 4276652 (1981-06-01), McCalmont et al.
patent: 4389671 (1983-06-01), Posner et al.
patent: 4398216 (1983-08-01), Field et al.
patent: 4410911 (1983-10-01), Field et al.

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