Winter Watchman helps prevent damage from cold or freezing temperatures by signaling neighbors that your heat is off. Simply plug the alarm into an electrical outlet located on an inside wall and plug a lamp into the alarm. Set temperature dial 10 degrees below your thermostat setting. When the room temperature drops below the alarm set-point， the lamp will light to warn your watchful neighbors to investigate. For incandescent use only. 120W/120V maximum. UL (Underwriter's Laboratories) listed.