ST series has AC and DC two input, and built-in auto transfer switch & syncronized operation with utility AC source/ ROF (Remote Override function) or ignition lockout function option/ Input & output fully isolation/ Power saving mode to save energy/ True Sine Wave output (THD<3%) / Capacity: 600W, 1000W, 1500W, 2000W and 2500W , DC voltage: 12V or 24V or 48V , AC voltage: 115V or 230V / Default prior to AC input, can change to prior in AC input when order (except ST600).