Abstract: A thermal sensor assembly is shown as having a housing formed of first and second body sections with the first being a probe-like portion for introduction into a medium the temperature of which is to be monitored; a thermistor and an electrical switch are electrically isolated from each other and situated within the housing; the thermistor is in series with and between one of the body sections and a terminal which is connectable to associated circuitry external of the sensor assembly; the electrical switch is effective to close an electrical circuit as between the same one of the body sections and a second terminal which is connectable to additional associated circuitry external of the sensor assembly.