Feature: Electrical and mechanical interlocks prevent cross connection of power sources. Quick change circuit board is easily replaced in the event of failure. No need to disconnect and reinstall the entire unit. Time delay ensures generator voltage is at a stable level before transfer occurs. The time delay can be disabled when an inverter is used as the alternate source. Rugged, heavy-duty, screw-type wiring terminals allow direct connection to contactor for more reliable operation. Heavy Duty metal enclosure with easy to use wiring diagram permanently attached. 1 year limited warranty.