JPS6481563A - Subscriber additional service system - Google Patents

Abstract

PURPOSE:To execute additional service other than telephone call when the telephone set is not in use without any circuit modification to the existing telephone sets and exchange by connecting a subscriber's side circuit and a station circuit in parallel. CONSTITUTION:The subscriber's side circuit 3 and the station inside circuit 4 are connected in parallel with the telephone set 1 and the subscriber circuit 5 of the exchange in parallel. In the station inside circuit 4, a caption S is a relay and a caption 41 is a window comparator to detect a voltage of the subscriber circuit, the insulation resistance of the subscriber line is not detected, and when the voltage drop of the subscriber circuit is larger by the DC loop current of the circuit 3, it is detected to activate the relay S. When the voltage drop is larger in the subscriber circuit 5 by the DC loop current by the telephone set, it is not detected and the relay 5 is restored. Thus, the additional service other than the telephone call is utilized regardless of the same subscriber line is used.