Patent
1975-03-20
1976-08-17
Safourek, Benedict V.
179 2R, H03K 1322
Patent
active
039756866
ABSTRACT:
A digital communication system employs delta-modulation coders and decoders for voice signal conversion. Signal inequalities at remote ends of a coder-decoder connection, due to unscheduled momentary interruptions of the transmission channel, are adjusted by insertion of a special pseudo-random "noise" signal at the remote demodulator. Voice Activity Compression (VAC) processing circuits, operating upon integrated digital signals which represent the analog (voice) input to the delta-modulation coder, are utilized to develop line activity indications. These indications are processed to produce VAC "channel use" information which is sent over a separate channel for remote demultiplexing control. The same activity indications are used to control remote demodulation handling and line level restoration. The remote control circuits insert the special pseudo-random signal at the remote demodulator during interruptions of the voice transmission (indicated as inactivity). The inserted signal adjusts the demodulator output level to correspond to the noise level at the input to the modulator. The demodulator signal is thereby reproducible as "natural" audible noise, consequently avoiding leaving the remote listener with the unnatural and disconcerting impression of a "dead" connection.
REFERENCES:
patent: 3131258 (1964-04-01), O'Neill, Jr.
patent: 3568061 (1971-03-01), Brolin
patent: 3647993 (1972-03-01), Foulkes et al.
patent: 3777066 (1973-12-01), Nicholas
International Business Machines - Corporation
Lieber Robert
Safourek Benedict V.
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