Circuit for call interception in telephone system - uses incoming call for sender actuation to send back AF signal causing transmission of calling subscriber code and number to store

摘要

A telephone system has a decentral control of selectors and interception devices. A first sender (S1) is allocated to the interception device. When an incoming call is made, it delivers backwards an a.f. signal. The first group selector stage (I.GW) has an additional device (ZE) with a first receiver (E1) for the above a.f. signal. On responding this receiver (E1) connects a second sender (S2) which transmits in an a.f. code through speech wires to the interception device the exchange code and the calling subscriber number obtained by the identification process. The interception device has a second receiver (E2) which receives these signals and transmits them to a store (Sp2).