PURPOSE: To enable to use a simple single-pole single-throw switch as selector switch, by providing an exclusive "OR" circuit between a temperature detecting circuit and a filp-flop circuit.

CONSTITUTION: Inverted input of comparator 8 is connected to junction A of resistance 2 and NTC-thermistor 3, whereas non-inverted input of the comparator 8 is connected to junction B of resistances 5 and 6. One input of exclusive OR circuit 24 is connected to output C of comparator 8, and other input of circuit 24 is connected to junction H of resistance 22 and switch 23. Ourput I of circuit 24 is connected to one input of NAND-circuit 19. Selector switch 23 for selecting either one of cooling operation or heating operation is designed to be turned ON at the time of cooling operation mode and turned OFF at the time of heating operation mode. When operation is necessary under either of the two operation modes, level of output I from circuit 24 becomes high for enabling operation of the air conditioner. In the above arrangement, it is enabled to use a simple single-pole single-throw switch by reducing the value of resistance 22 to great extent.