It include a transformer and an inverter. the variable transformer automatically adjusts the secondary winding taps as the input voltage varies. This voltage regulation feature allows the UPS to adapt to a wide range of high and low voltage conditions without switching completely to the backup power. This extends the UPS and its battery useful life. High efficiency, small size, low cost, high reliability, and the ability to correct low or high line voltage makes this UPS type dominant for the 0.5 KVA - 5 KVA range of devices.