Cryptography – Cryptanalysis
Patent
1993-01-06
1994-03-22
Ng, Jin F.
Cryptography
Cryptanalysis
380 23, 379 62, 379 61, 370111, H04M 1106, H04K 100
Patent
active
052972038
ABSTRACT:
A digital cordless telephone apparatus comprising a microprocessor based battery powered portable handset unit and a microprocessor based stationary base unit which each transmit and receive digital voice data and digital command data to and from one another over multiple RF channel frequencies in the 902-928 MHz band, is disclosed. The user's voice is digitized, scrambled and modulated for transmission and upon reception, the modulated digital voice data signal is demodulated, descrambled and decoded. A command data - voice data interface inserts command data packets into the stream of digital voice data prior to transmission and locates and captures command data packets from the incoming stream of received digital data. A silence sequence replaces the captured command data packet such that no audible sound is heard by the user. A link check command signal is also periodically transmitted by the base unit and acknowledged by the handset unit to evaluate the quality of the RF link toward triggering an automatic channel change or signaling an out-of-range condition.
REFERENCES:
patent: 4663765 (1987-05-01), Sutphin et al.
patent: 4813040 (1989-03-01), Futato
patent: 4939785 (1990-07-01), Murata et al.
patent: 4972510 (1990-11-01), Guizerix et al.
Heung Charley
Rose Chris
Bost Dwayne D.
Ng Jin F.
Video Technology Engineering, Ltd.
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