PURPOSE: To simplify the constitution and operation of the device by a method wherein respective rooms are provided with one set of operating switch and monitoring means to cope with a plurality of terminal control units and air- conditioning machines so that abnormality in even one set of them is informed, in case one room is provided with a plurality of terminal control units and air- conditioning machines.

CONSTITUTION: In case two sets of air-conditioning machines (n), (n+32) are installed in one room, the signals of operating conditions of both slave air- conditioning machines (n), (n+32) are inputted. In this case, the operation command lamp 16 is lighted only when both of the slave machines (n), (n+32) are being operated and the other lamps are put OFF under a condition that the operation command lamp 15 of number n is being lighted and the n slave machine is under receiving the operation command. A monitoring lamp 16 of n is put OFF only when both of the slave machines (n), (n+32) are being stopped but the same lamp is lighted in case either one of them is being operated. Thus, abnormality is informed when either one of the machines is operating in different manner from the command and the constitution as well as the operation of the device may be simplified.