A two-wire teleconferencing terminal

Based upon the studies implemented by the Department of Communications, a two-wire teleconference desk set is proposed employing conventional moving-coil loudspeakers as bi-lateral transducers. The low electro-acoustic efficiency of these transducers is significantly increased by the use of a balanced positive feedback arrangement. Four moving-coil loudspeakers are interconnected with a conventional two-wire to four-wire termination to produce an overall terminal which is genuinely two-wire in operation. The resulting prototypes produce acceptable levels for both sending and receiving in an office-to-office situation and can be connected in a multi-party mode. This eliminates many of the undesirable features of the currently available voice-switched loudspeaking telephone sets.