| 摘要 |
PURPOSE:To always monitor the presence or absence of the disconnection and the short-circuit of the control line, by giving the termination to the control line via the diode along with application of the alternating pulse voltage and then detecting the change of the pulse voltage at the point of application through the disconnection/ short-circuit detecting circuit. CONSTITUTION:Diode D is connected between the terminal of control line L and common control line LC of disaster preventing facilities M, and the alternating pulse voltage generated from pulse generating circuit PG is applied to line L via current limit resistance R1. When a short-circuit fault occurs to line L, no pulsating pulse voltage is applied to application point A of the alternating pulse voltage. Thus transistor T1 is cut off, and short-circuit display lamp LA is lit up. At the same time, power supply E is not given to line L. In the case of the disconnection fault, the alternating pulse is applied to point A. And thus FETT2 conducts to light up disconnection display lamp LB with no power supply E given to line L. In such constitution, the presence or absence of the disconnection and the short-circuit can always be monitored. |
