*This product adopts the anti-phase integrated circuit and sampling control to control the electromagnetic relay and change the varitran's tap for the purpose of stable output voltage.* This product has a wide range of input voltage, which can ensure output voltage 220V±10% when the voltage of mains supply changes within 150V～270V. *Also it's provided with time delay output and overvoltage protection, which can effectively protect safe operation of air-conditioner and refrigerator compressors. *It has a fast adjusting speed and the overall efficiency is up to over 95%.