| 摘要 |
PURPOSE:To simplify the constitution of a ring trip circuit and to detect the answer of a subscriber telephone, by connecting an optical coupling element and a rectifier to a call signal transmission line, and then detecting the continuity of the optical coupling element. CONSTITUTION:Lines A and B are connected to a telephone TEL, and a call signal device S and an optical coupling element PC are set to a contact g<0> of a call signal transmitting relay. A diode D is connected to the element PC, and the output of the element PC is used as a continuous signal, then inverted by an inverter GTO to be applied to a resettable delay pulse generator DPG. The continuity of the element PC is detected by the output of the generator DPG, and the answer of a subscriber telephone TEL is detected from the continuity. Then the relay F is actuated to stop the call signal. Thus the constitution is simplified for a ring trip circuit of an automatic telephone exchange. |
