PURPOSE: To inspect at the times of installation, maintenance service while staying at the side of an outdoor unit by executing and stopping normal operations of the outdoor unit and an indoor unit in response to the operation of trial operation actuating means provided in the outdoor unit.

CONSTITUTION: A pushbutton switch (normal open contact of an automatic reset type) 14 is provided as trial operation actuating means in an outdoor unit A, a DC constant voltage Vd is applied to the switch 14 through a resistor 13, and a mutual connection point of the resistor 13 to the switch 14 is connected to the input port Pi of an outdoor controller 10. The controller 10 is connected to an indoor controller 20 via a power source voltage synchronization type serial signal line SL to transmit data between both the controllers. When the switch 14 is pressed, an input of the port Pi of the controller 10 becomes an 'L' level, and is set to a trial operation mode. Thus, a series of processes regarding an inspection work can be performed while staying at the side of the unit A without going to the unit B side at each time.