Multiplex communications – Wide area network – Packet switching
Patent
1981-12-17
1985-07-09
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
179 2DP, H04J 602
Patent
active
045286590
ABSTRACT:
The disclosed invention allows digital data to be integrated with a digital voice signal in a simple manner that does not affect the voice transmission quality. Digital data is inserted in quiet or "no speech" portions of the voice signal stream when such quiet periods are detected. No flags, headers, or other indications are necessary upon the insertion of digital data. The digital data is encoded in a two byte pattern in which the scaling bits are set high and the sign bit alternates in each eight bit byte. Four bits of each byte are thus reserved for scaling and sign purposes, but the remaining four bits are available for data transmission. Setting the three scaling bits high and alternating the sign bit has the effect of indicating to the receiver that voice is not present. This is so because the scaling bits and alternating sign bit will be decoded under the PCM coding technique to indicate an out of scale four kilohertz tone that is not allowable within the transmission path requirement of the Bell System or the CCITT in Europe. Recognition of such a signal by the receiver permits a detector to block the output at a speech terminal and to strip the scale bits from the input two byte patterns and pass the remaining bits as data to a data output.
REFERENCES:
patent: 3303285 (1967-02-01), Brown
patent: 3760106 (1973-09-01), Monti
patent: 3882280 (1975-05-01), Goutmann
patent: 4394757 (1983-07-01), Muzumdar et al.
T. Kishimoto et al., "Simultaneous Transmission of Voice and Handwriting Signals: "Sketchphone System", IEEE, 1981, pp. 1982-1986.
R. C. Smith et al., "Voice/Data Concentrator", IBM Tech. Disc., vol. 21, No. 8, Jan. 1979, pp. 3066-3067.
Patent Abstracts of Japan, vol. 4, No. 141, 10-4-1980, p. 60E28; & JP-A-55 92 068 (Fujitsu K. K.) (12-7-80) Abstract.
Chin Wellington
Duffield Edward H.
International Business Machines - Corporation
Olms Douglas W.
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