Cutting-edge technology sends fast alerts that give your family more time to get out safely, & enhanced sensing technology reduces false alarms often caused by cooking. When its photoelectric sensor is triggered, the Detect Smoke Alarm features a red LED that flashes in sync with three long beeps. The alarm repeats the pattern until the unit is reset or the smoke is eliminated. Alarm memory alerts you if smoke has been detected in the last 24 hours. Alarm runs on two AA replaceable batteries (included) for continual detection even during outages & alerts you to both smoke (photoelectric sensor). Self-testing alarm is easy to install with the included twist-and-click mounting bracket. Low-battery indicator is one chirp & an amber flash per minute. Equipped with end-of-life notifications, the flashing red alarm will beep to remind you it's time to replace it 10 years after it is powered.