Don't get caught with your voltage down! Solid state reliability with no moving parts for quality you can count on. Autoformer provides protection from low voltage damage by boosting the park voltage to your RV! "Sense circuit" automatically turns the 10% boost on when the park power is less than 117 volts and turns it off when the park power reaches 118 volts. Built in grounding continuity test offers protection against damage from open ground, open neutral or reverse polarity - if the light isn't on, do not use the power source! Installs into your RV electrical system (with the optional installation kit 55-3982) or plugs into the park's power pole. 30 Amp Autoformer. Three year limited warranty. 1 per box.