A handy way of controlling any electrical device up to 15 amps. The attached device can turn ON or OFF when power is applied to the relay (your choice). For example, you could roll your projector screen down when your stereo is powered up. Or turn your furnace on when the the lights go out. The output terminals are "dry contacts", which means they wire up just like an ordinary switch. The product contains a high power relay, circuit breaker, and safety circuit that are triggered by external AC power.