Patent ID: 8042345

Claim:
An air conditioning system comprising: an indoor unit and an outdoor unit connected to each other through common power supply lines; the indoor unit comprising: a first communications circuit configured to perform communication with the outdoor unit through at least one of a first communication line and a second communication line independent of the common power supply lines; a second communication circuit configured to perform communication through at least one of the two common power supply lines and a third communication line independent of the at least two common power supply lines; the outdoor unit comprising: a third communication circuit, having a communication terminal, configured to communicate with at least one of the first communication circuit and the second communication circuit; a switch configured to connect or disconnect the communication terminal of the third communication circuit and one of the common power supply lines on the basis of a connection status between the third communication circuit and each of the first communication circuit and the second communication circuit; and a judging circuit configured to control the switch connection and disconnection, and further configured to transmit a predetermined signal to the indoor unit, wherein the judging circuit is further configured to judge, based on the presence or absence of an acknowledge signal from the indoor unit, whether the first communication circuit and the second communication circuit is connected to the outdoor unit.