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Browse Prior Art Database

Voice and Data Transmission

IP.com Disclosure Number: IPCOM000050467D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Gergaud, C: AUTHOR [+2]

Abstract

This is a technique for multiplexing voice and data signals over the same digital transmission link, using SDLC (Synchronous Data Link Control) techniques. Though proposed for a single voice channel, the method may be extended to several channels. The technique is based on the pause compression method.

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Voice and Data Transmission

This is a technique for multiplexing voice and data signals over the same digital transmission link, using SDLC (Synchronous Data Link Control) techniques. Though proposed for a single voice channel, the method may be extended to several channels. The technique is based on the pause compression method.

Data are transmitted per messages of 6 to 256 characters, having the following format: F, A, C, D, D...D, B, C, F. wherein: F = Flag, A = Address,

C = Control characters,

D = Data bytes, and

BC = Two block check characters.

Digitalized voice can be divided into periods of activity and periods of silence. During the activity period, the data bytes can be grouped in messages having the following format: F, A, S, V, V...V, F. wherein: F = Flag, A = Voice channel address,

V = Voice data bytes, and

S = Silence counter.

During the silence periods, nothing is transmitted, but the silence time is computed and its value is transmitted in the next voice message. The silence time permits synchronization to be kept between the voice coder at one end and the voice decoder at the other end.

A PCM coder transmits 8,000 bytes per second. During a period of 20 milliseconds, it transmits 160 bytes (20 bytes with a compression factor of 8) which can be taken as the basic voice message.

When during a period of 20 milliseconds there is voice activity, a voice message is transmitted.

When there is silence during a period of 20 milliseconds, a "one" is added to the silence counter and nothing is transmitted.

The silence counter indicates at the other transmission end the time which separates the successive voice messages. This time must be very precise between phonemes and words, bu...