JPS56122580A - Line terminating system of time division telephone switchboard - Google Patents

Abstract

PURPOSE:To reduce the transmission loss of a switchboard by providing with a matching circuit for matching the impedance of the converting circuit, and a building-out network for balance maintenance, on the time division switchboard equipped with a two-wire-four-wire transducer. CONSTITUTION:When a subscriber has requested a call by mean of off-hook of a telephone set 1, the electric power source 18 supplies the power to the telephone set 1, this current value is detected by the DC detection circuit 22 consisting of a Hall element, it is informed to the building- out network control unit 28 consisting of a microprocessor, and a constant of the control unit 25, which is suitable for the subscriber's line 2 is selected under control of the unit 28. A service current from the telephone set passs through transformer 15, the line balance stat is improved by the control unit 25, transmission and receiving are separated by the hybrid HYB29, and the line balancing and impedance matching are executed by the balance connection network 32. Also, a transmitting current is encoded and decoded by the encoder and decoder 35, and the converting operation is executed by the time division switch 38. The unit 28 stores the station data of a kind of line, a cable system, etc. as a balance condition, and controls by calculating an optimum constant of the control unit 25.