In event of a power failure, the wireless ReadyBright Power Outage Lighting System immediately turns on all its companion battery-operated emergency LED lights installed within 70 feet of the controller unit/detector (that's been plugged into any outlet). Each light will reportedly stay lit some 40 hours on one set of batteries. The system kit includes one power outage detector, three stairway/pathway (hallway) lights, and three ceiling lights. (The detector can reportedly activate up to 30 lights, if need be.) System setup is similar to installing a battery-operated smoke alarm.