Cryptography – Communication system using cryptography – Wireless communication
Patent
1991-08-12
1993-01-19
Cangialosi, Salvatore
Cryptography
Communication system using cryptography
Wireless communication
H04K 100
Patent
active
051812460
ABSTRACT:
A privacy communication device uses a control channel (5) in addition to a voice channel (4) in communicating with other privacy communication device. Each privacy communication device employs a ring modulator (8) and a ring democulator (14). A specific modulator carrier frequency to be given to the ring modulator (8) is selected by function of a control signal transmitted on the control channel (5) out of a plurality of modulator carrier frequencies prepared in advance. Likewise, a specific demodulator carrier frequency to be given to the ring democulator (14) is selected by function of a control signal transmitted on the control channel (5) out of a plurality of demodulator carrier frequencies prepared in advance.
Hence, when the specific modulator carrier frequency and the specific demodulator carrier frequency are updated at arbitrary intervals, a third person cannot easily identify the varied modulator carrier frequency and demodulator carrier frequency. Thus, secrecy of a voice signal transmitted through the voice channel (4) between the two privacy communication devices is enhanced.
REFERENCES:
patent: 4068094 (1978-01-01), Schmid et al.
patent: 4188506 (1980-02-01), Schmid et al.
patent: 4525844 (1985-06-01), Scheuermann
patent: 4790009 (1988-12-01), Ishigaki et al.
Cangialosi Salvatore
Mitsubishi Denki & Kabushiki Kaisha
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