Loop on-off state detection device and method

The invention discloses a loop on-off state detection device and method. A detection signal is sent to a detected loop contact point and a detection signal isolation coupler through an isolation capacitor I; the detection signal isolation coupler receives a feedback signal of the detected loop contact point through an isolation capacitor II, couples the feedback signal with the received detectionsignal, and sends a coupling result to a detection signal receiving processor; the detection signal receiving processor analyzes the coupling result, and if the detection signal receiving processor receives the detection signal, it is considered that the detected loop contact point is in a conducting state, otherwise, the detected loop contact point is in a disconnected state. The detection process does not need to depend on the state of a detection object, is direct detection, and does not need to be realized by virtue of state parameters, such as voltage, current and temperature of the detected loop contact point or