Dual telephone connection using single line - includes two six-contact relays in parallel to latch one telephone onto line and isolate second telephone

摘要

Each telephone unit possesses a buzzer, and a pushbutton switch. Two biassed conductors are connected to the wires of the line via a four diode bridge. Two unbiassed conductors are connected directly to the wires of the line. On one of the biassed conductors there is a first six-contact relay. In parallel with this relay is a second six-contact relay. After one telephone set has been taken off the hook, the operation of the corresponding pushbutton ensures a supply to the relay corresponding to this telephone. This also connects the telephone on to the line, and isolates the other telephone. Capacitors are connected in parallel to the buzzer to eliminate parasitic interference.