<p>A temperature responsive apparatus includes a thermocouple producing a thermoelectric e.m.f. depending on the temperature difference between a temperature to be detected and a circumferential temperature and a first winding supplied with current from the thermocouple to generate a first magnetic field. A second winding is connected to a voltage source to generate a second magnetic field in the opposite direction to that generated by the first winding and a reed switch is positioned in the total magnetic field generated by the first and the second windings so as to respond to the intensity of the total magnetic field to make and break its contacts. A diode is also connected to the voltage source, and the second winding is always excited in accordance with the voltage drop across the diode to maintain said second magnetic field.</p>