Current flows from the external terminal through the bimetallic strip, then to the base plate terminal to form a circuit with the appliance (e.g., motor, transformer, etc.). When abnormal operation of the appliance causes excessive ambient temperature, the heat transfers to the bimetallic strip. Upon reaching the calibrated trip temperature, the bimetallic strip rapidly opens the electrical contacts, cutting off the circuit. When the temperature drops to the reset temperature, the bimetallic strip resets and quickly closes the electrical contacts, restoring the circuit. This cycle repeats as needed.