SELECTIVE RINGING IN SUBSCRIBER CARRIER TELEPHONE SYSTEM

摘要

Selective ringing for two subscribers who share a single channel in a subscriber carrier telephone system. The ringers at the subscribers' subsets are connected respectively between ground and the ring lead for one subscriber and between ground and the tip lead for the other subscriber. When the central office switching equipment applies a ring signal between its outgoing tip lead and ground, the terminal equipment at the central office transmits both the ring signal and a 1.1 kHz. tip identification signal on the outbound carrier signal. The terminal equipment at the subscriber end of the line detects the identification signal and operates a relay in response to it to cause the output of the "ring" amplifier to be applied between the tip lead and ground. In the absence of the identification signal, the output of the "ring" amplifier is applied between the ring lead and ground.