By separating the compressor and condenser coil from the fan and evaporator coil, the noisiest component is away from the room. The indoor unit will usually have remote control capabilities and a timer to cycle the system only when needed. The indoor unit is called an air handler because it has the evaporator coil, blower, and controls inside. The outdoor unit is called the condenser. They are connected together with refrigerant piping and control wiring, similar to a central system.
Some manufacturers use low voltage to control the system, others use line voltage.
Caution must be taken when opening up the cabinet to shut power off when servicing. The most important service item is dirt. Screens or filters can usually be found behind the front grill of the air handler. Tabs allow them to slide out for cleaning. Keep vegetation and debris away from the outdoor unit to allow good air flow for maximum cooling efficiency.