120-volt AC (alternating current) smoke detector uses an ionization smoke sensor to reliably detect smoke from hot， fast-flaming fires and alerts you with a loud 85-decibel alarm. Designed to be wired directly into home's electrical system， features a backup battery that helps keep the alarm functioning even in the event of a power outage. Battery life varies according to use and application. Gasket-less mount helps ensure a perfect alignment for easy installation， while tamper-resistant locking pins keep the alarm secure. Includes a convenient test/silence button， to easily check whether the alarm is functioning properly and mute false alarms. Integrates with up to 12 other First Alert or BRK hardwired alarms and features a latching indicator that identifies which unit triggered the alarm.