This transformer is designed to plug directly into a powered outlet, eliminating the need of building a special transformer enclosure. It contains a built-in thermal circuit breaker, making it virtually burnout proof. In the event of an overload or short, the thermal breaker simply opens and removes voltage until the unit cools. After cooling, the breaker resets itself and automatically reapplies voltage to the output. The 12V/20W Plug-in Transformer outputs DC current.