X-SENSE Photoelectric Smoke Alarm - 2 UnitsEnhanced performance and earlier hazard warning compared to most non photoelectric sensor devices. Red LED flashes every 43 seconds in standby status and flashes quickly when alarming. Over 85dB loud alarm sound to alert all members in the household when smoke is detected. Can be easily mounted on the ceiling using the provided mounting bracket, screws and anchor plugs. Powered by a 9V alkaline battery (Included) that offers a 3 year life.