Engineering Aspects of TASI

The number of telephone circuits carried by a submarine cable system can be doubled by using the normal gaps in speech to interpolate additional conversations. TASI is a high-speed transmission and switching system that assigns a talker to a channel as soon as he starts to talk and disconnects him when he pauses, if someone else needs the channel. Switching from channel to channel may occur many times during a typical call, but the effect on transmission quality is negligible because the switching time is fast compared with the syllabic rate. For many years telephone people have been intrigued with the idea of making use of the idle time during a telephone call. TASI, an abbreviation for Time Assignment Speech Interpolation, is a high-speed transmission and switching system based on the principle of using the free channel time to interpolate additional talkers. Although TASI requires considerable terminal equipment, it can approximately double the usefulness of long, expensive channels such as the deep sea submarine cable systems. The first speech interpolation system is expected to be placed in service during 19G0 on the transatlantic telephone cable system between London and New York that was opened for service in September 1956. The basic principles of TASI are old. An extensive investigation of the feasibility of speech interpolation systems was conducted in 1946 and 1947 by A. C. Dickieson, P. G. Edwards and others. An experimental model was demonstrated in 1950 by A. E.