A monitoring circuit includes a configuration interface, a control circuit, a detection circuit, a direct current voltage source, a switch circuit, and a first resistor. A first end of the configuration interface is separately connected to the direct current voltage source and an input end of the switch circuit; a second end of the configuration interface is separately connected to a first end of the first resistor and an output end of the switch circuit; a control end of the switch circuit is connected to the control circuit; a second end of the first resistor is grounded; the detection circuit is connected to the first end of the first resistor; the configuration interface is configured to connect to a dry contact; the control circuit controls closing or opening of the switch circuit; and the detection circuit detects a voltage between two ends of the first resistor.