Abstract: A recognition process for an air conditioner is executed while the deterioration of the environment due to stoppage of the air conditioner is suppressed. In an air-conditioning system in which a plurality of air conditioners belonging to an identical refrigerant system are connected through a communication line inside the identical system and a plurality of air conditioners belonging to different refrigerant systems are connected through a communication line outside the different systems, for the plurality of air conditioners belonging to the identical refrigerant system, a recognition process is executable while an air-conditioning control process is executed by transmission through at least the communication line inside the system.