PURPOSE: To detect the abnormal state of a temperature sensor in its early stage by receiving a radiation signal from the temperature sensor which corresponding to detected temperature, and detecting and display the reception state.

CONSTITUTION: A mixer 19 with a local oscillator 20 is connected to an antenna 17 through an RF amplifier 18, the output of a frequency counter 21 connected to the mixer 19 is connected to a part 22 whose temperature is to be controlled, an AND gate 23, and a NAND gate 25, and a power source 241 is connected to the other-terminal sides of the gates 23 and 25. Further, a display device 24 is connected to the gate 23 and an auxiliary temperature sensor 26 is connected to the gate 25 respectively to set the set temperature of the control part 22 with the output of the sensor 26. Then, a radio wave of oscillation frequency corresponding to the temperature from the sensor 11 is received by the antenna 17, the display device 24 turns off when the frequency output detected by a counter 21 is not detected any more, and the set temperature of the control part 22 is controlled through the sensor 26 with the output of the gate 25.