Data and speech transmission system using 4-wire telephone cable - has respective line wire pairs for transmission of speech and data signal in opposite directions between speech points and exchange

摘要

The transmission system allows transfer of data and speech signals between a number of speech points (42, 44, 46) and a central exchange (10). Each of the speech points is connected in parallel to a telephone cable (36) with 2 pairs of wires respectively used for transmission from an output circuit (22) of the exchange to the speech points and for transmission from the speech points to the exchange output circuit. The current supply of the speech positions is effected via both wire pairs. One or more power amplifiers (45,47) are connected for data and speech transmission in the telephone cable. Each amplifier is connected to the current supply by a pair of wires and uses min. quiescent current. ADVANTAGE - Requires single 4-wire telephone cable. Min. maintenance requirements in areas where inaccessible, or even no, subscriber power supply exists.