Speech Interpolation in Digital Transmission Systems

In a telephone conversation a channel is activated by the voice only 25 percent of the time. It is therefore possible to provide a number of connections with a number of channels, where is less than . When the number of connections is large, (gain) tends to the inverse of the activity. The interpolation procedures used in overload conditions and the resulting degradations, as well as the typical circuits of a voice interpolation apparatus, are examined. Also, two very highly interesting developments are herein illustrated, the ATIC equipment and a single-channel digital speech interpolation (DSI) developed only for measurement purposes. The results obtained from measurement studies carried out with the aforementioned apparatus have enabled the determination of the criteria which must be followed in the selection of the most suitable interpolation procedures. Besides examining the complexity and the reliability which the DSI equipment calls for, it has been possible to analyze the precise working characteristics under normal operating conditions.