PURPOSE: To attain a switching system for the power supply of a local oscillator with a remote control operated by an indoor unit, by changing the level of power supply voltage for the local oscillator supplied to an outdoor unit from the indoor unit to switch the supply destination of the power.

CONSTITUTION: Transistors Tr1 and Tr2 of an outdoor unit 14 constitute a differential amplifier. When the base voltage of the Tr1 is higher than the base voltage of the Tr2; the TrQ and TrB are turned on and off respectively. Then the output power of a constant voltage circuit 16 is supplied to a local oscillator 33 only. While the TrA and TrB are turned off and on respectively, and the output power of the circuit 16 is supplied to a local oscillator 34 only. The base voltage of the Tr1 is set at a level according to the change of the power supply voltage supplied from a power supply circuit 11 of an indoor unit 10. While the base voltage of the Tr2 is kept at a fixed level. In such a constitution, the drive voltage is switched to only one of oscillators 33 and 34 by changing the output power supply voltage of the circuit 11 to high and low levels by a voltage switching circuit 12.