Circuit arrangement for telecommunications switching systems, particularly telephone switching systems with space-division multiplex switching equipment and equipment for searching subscriber line circuits which are in the call state

摘要

In a telephone switching system with space-division multiplex switching equipment (RT, R12, R3, R4) and equipment for searching subscriber line circuits (TA) which are in the call state, four-wire-connected subscriber line circuits output a call signal as PCM word via the forward channel. An adjusting device (ST) selects a free junction circuit (V12) with dial code receiver (EV) and cyclically successively connects itself via subscriber switching stage (TK:RT) to all subscriber line circuits (TA). If it receives a call signal, it leaves the relevant connection up and selects another free junction circuit and uses this to continue the search. The connected junction circuit (V12) outputs (SR) call signal acknowledgement signals via the backward channel to the subscriber line circuit (TA) as a result of which the call signal is ended, and thus also the call signal acknowledgement signal. IMAGE