| 摘要 |
PURPOSE:To enable the discrimination of states by outputting a half-wave rectification voltage opposite in the polarity between the operations of alarming and monitoring to cause a short-circuiting of the half-wave rectification voltage during the normal monitoring in case of the interruption of a power source. CONSTITUTION:In the normal monitoring, a switching contact ry1 is turned to the position of a positive half-wave rectification circuit 10a while a normally open contact ry2 is open. Under such a condition, a positive half-wave rectification voltage is outputted to output terminals O2 and O2 of an alarm output circuit 7. Then, when a detection output is sent from a detection circuit detecting gas, a relay Ry1 is operated to switch the switching contact ry1 over to a negative half-wave rectification circuit and a negative half-wave rectification voltage is outputted. When the power source of a gas leak alarm 4 is interrupted for some reason or other, the power source relay Ry2 is restored and the normally open contact ry2 is closed and the gas leak alarm is short-circuitted. In this manner, the positive half-wave rectification voltage at the monitoring, the negative half-wave rectification voltage at the alarming and zero voltage by the short-circuiting in case of the interruption of the power source are given and can be detected with a receiver. |
