The BRK 9120B Hardwired Smoke Alarm with Battery Backup. This 120 volt AC 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 your home's electrical system, this hardwired smoke detector features a backup battery that helps keep the alarm functioning even in the event of a power outage. The gasket less mount helps ensure a perfect alignment for easy installation, while tamper resistant locking pins keep the alarm secure. And thanks to the convenient test/silence button, you can easily check whether the alarm is functioning properly and mute false alarms. This smoke alarm can integrate with up to 12 other First Alert or BRK hardwired alarms and features a latching indicator that identifies which unit triggered the alarm. Hardwired ionization smoke alarm with 9-volt battery back-up Latching alarm indicator - remembers which unit initiated an alarm Two silence features - can silence the low-battery chirp for up to eight hours or temporarily silence an unwanted nuisance alarm Easy installation and maintenance 10-Year limited warranty Tested to meet UL standards