| 摘要 |
PURPOSE:To detect the existence of irregurality and to execute processing such as the stop of calling when the irregurality is detected, by supervising a subscriber's line which is not permitted as a free line and detecting the existence of a response signal at the terminating to the subscriber. CONSTITUTION:When a calling signal is terminated to a subscriber's telephone (TEL) through a switch frame SWF, a terminating discrimination relay TER is actuated and a relay R receiving the calling signal from an incoming trunk is connected between lines A and B. When the relay R is actuated after receiving the calling signal from the incoming trunk, a subscriber calling relay G is actuated and a calling signal IR is sent to the subscriber's TEL through a contact (g). When the subscriber's TEL responds to the calling signal, a relay F is actuated by a call stopping signal. The actuation of the relay F restores the relay G and the call stopping signal is sent to the incoming trunk by a DC loop passing through a contact fa, a diode D and a line L. |
