Abstract: An air-conditioning system operable at different states employs a control unit including a receiver and a transmitter. The receiver is connected electrically to a switching device for a compressor of the air-conditioning system. The compressor is installed at a remote location exterior to a building. The receiver is responsive to an encoded radio signal to provide an electronic control signal for actuating the switching device. The transmitter is installed within the building and is electrically connected to a thermostat within the building that responds to temperature changes to provide a temperature control signal. The transmitter upon receipt of the temperature control signal transmits to the remote location the encoded radio signal for operating the air-conditioning system at one of the different states.