Current flows from the housing terminal, through the bimetallic strip, and then to the base plate terminal, connecting to the electrical appliance (e.g., motor, transformer, etc.) to form a circuit. When abnormal operation of the appliance raises the ambient temperature excessively, heat is transferred to the bimetallic strip. Once it reaches the calibrated trip temperature, the electrical contacts quickly open, cutting off the circuit. When the temperature drops to the reset temperature, the bimetallic strip resets and rapidly closes the electrical contacts, re-establishing the circuit, and the cycle repeats.