Electronic system for the secret transmission of audio signals

Details Electronic system for the secret transmission of audio signals Electronic system for the secret transmission of audio signals

1983-01-24

1987-04-21

Buczinski, S. C.

Cryptography

Key management

Having particular key generator

380 20, 380 21, 380 38, 380 48, H04M 170

Patent

active

046598758

ABSTRACT:
System for the secret transmission of audio signals having at one end a coding arrangement comprising an input low-pass filter which selects the secret audio signals to be transmitted, two parallel signal paths at the output of this filter, each path having a modulator of the phase-inverting type and a further low-pass filter, a stage for generating two modulation signals of the frequencies F.sub.1 and F.sub.2 and a first change-over switch which alternately switches through the output of the two paths in dependence of the state of a binary quasi-random signal, the encoded audio signals to be transmitted being available at the output of the change-over switch, and in which at the other end there is a decoding arrangement comprising a stage for regenerating the modulation signals of the said frequencies F.sub.1 and F.sub.2, a second change-over switch which alternately switches through one of these two modulation signals in dependence on the state of a binary quasi-random signal which is synchronized with the binary quasi-random signal used in the coding arrangement, followed by a demodulator for the audio signals and a low-pass filter for selecting the decoded audio signals.

REFERENCES:
patent: 1502889 (1924-07-01), Van Der Bul
patent: 2407259 (1946-09-01), Dickieson
patent: 3610828 (1971-10-01), Girard et al.
patent: 3777064 (1973-12-01), Allen
patent: 4159399 (1979-06-01), Asakawa
patent: 4188506 (1980-02-01), Schmid
"Transmission Systems for Communications", Members of the Technical Staff, Bell Telephone Laboratories, 1971, pp. 97, 125-127.

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