| 摘要 |
PURPOSE:To simplify the installation work of the titled device and to decrease an operation mistake, by connecting two detecting elements moving in response to one polarity, to a line by making the elements reverse in polarity each other. CONSTITUTION:When an outgoing request is given from a terminal device, a CPU100 operates an S relay to lead in subscriber lines L1, L2 from an exchange to a line polarity monitor 102. When the subscriber lines are idle, the line L1 is a ground level, an LEDD2 is made conductive to form an outgoing loop, and a transistor(TR) Q2 is made conductive. Since the polarity of the lines L1, L2 is inverted with an incoming call from the exchange, the LEDD2 is not made conductive, an LEDD1 is made conductive to form a DC loop. Since a TRQ1 is made conductive in this case, the CPU100 recognizes the incoming call through the lines L1, L2 from the exchange. The exchange detects the forming of the DC loop and restores the polarity of the lines L1, L2. Thus, the LEDD1 is made nonconductive and the LEDD2 is made conductive, resulting that the TRQ1 is also made nonconductive. |
