It can control indoor&outdoor fan speed,electric heater,compressor,valve, sweep etc. a. Low cost b. Apply 8 bit microcomputer of NEC or ... 7segments LEDs or LCD(backlight) or VFD f. It can control indoor&outdoor fan speed,electric heater,compressor,valve, sweep etc ... . g. The power line communication is applied between indoor and outdoor controller h. It can run cool,heat,fan,dehumidify ...