4F AC protector comes under the automatic voltage stabilizer that is a microprocessor based system. It controls the operations as well as protects one air conditioner and its compressor from any electrical damage caused by under voltage, under load, over voltage, over load. The front panel has LED light to indicate faults when occurred. It consumes less power and operates for years without the need of any kind of repair. Contact us to know more about the specifications, such as power on delay time,restart delay time and trip time delay.