Two-Circuit MonoRail Surface Transformer-500W Mag. This single-feed surface transformer converts standard 120 line-voltage to 12 volts to provide the necessary voltage for powering a Two-Circuit MonoRail low-voltage lighting system. It can power lamps totaling up to 500 watts with 250 watts maximum on each circuit. The transformer is concealed inside a decorative housing with a fast acting secondary circuit breaker that will safely turn the system off should a short occur. Once the short has been removed the breaker can be reset.