Multiple telephone party lines connector for exchange lines - couples decentralised-locking telephones using overall loop current detector with AC by=pass capacitor and relay contacts for bridging during conversation

摘要

The telephone subscriber's appts. (A1-A4) are connected pairwise (11,17) to the exchange line (La,Lb) via loop current detectors (S1-S4) whose control signals are AND-gated with that of an overall loop current detector (34) bypassed for AC by a single capacitor (38) of 470 microfarads and a protective diode (39). The combinatorial switching is performed by selective activation of setting windings (K1-K6) which have a switching transistor (26) in their common supply line, not operative during the calling phase. Bridging by contacts (K5,K6) eliminates attenuation during the speaking phase. ADVANTAGE - Space requirement for AC bridging equipment is reduced with fewer bulky capacitors.