• A Fixed Sampling Rate Vocoplexer

      Lerner, Theodore; Textron Bell Aerospace (International Foundation for Telemetering, 1975-10)
      The vocoplexer is a system which permits a reduction in the data rate required to transmit voice signals when many such signals are multiplexed onto a common digital line. This is accomplished through the use of a coding technique which is based on the statistical properties of voice signals. The reduction in data rate that can be realized by the vocoplexer is a function of the speech quality required. Typically, for a speech quality equivalent to PCM at 8,000 samples per second and five bits per sample, a reduction in data rate to about 1/3 can be accomplished. The descriptions in this paper are based on this quality requirement. However, for a somewhat reduced quality requirement, even greater savings can be accomplished. For example, if quality equivalent to PCM at 8,000 samples per second at four bits per sample is adequate, the vocoplexer will require approximately 9,600 bits per second. For quality equivalent to delta modulation at 18,000 bits per second the vocoplexer requires approximately 6,400 bits per second per voice channel.