First Alert BRK Brands 9120B Hardwired Smoke Alarm with Battery Backup 4 Pack

The revolutionary BRK 9120 series smoke alarms have been redesigned from the ground up. They install faster, perform better, and are even smarter than before. All of these improvements help reduce nuisance alarms and save time and money. BRK Electronics' smoke alarms are designed to be easy to install, easy to maintain, and quality-engineered for years of virtually maintenance-free service. The 9120B includes an ionization sensor which helps detect fast flaming fires that consume combustible materials rapidly and is 120-volt AC inter-connectable (with maximum 18 compatible devices), which lets the alarm be interconnected with up to 12 other compatible smoke alarms and six compatible devices like bells, horns, repeaters, and door closers. If one unit triggers an alarm, all smoke alarms in the series will sound. Power indicators show which unit in the series initiated the alarm and a latching alarm indicator automatically identifies which unit initiated the alarm. This is smart technology to reduce nuisance alarms. It also has a 9-volt battery backup for peace of mind during power malfunction, a single test/silence button which both silences a non-threatening alarm or low battery warning and allows you to test the unit's functionality, a perfect mount system, including a gasket less base for easy installation and new mounting bracket that keeps the alarm secure over a wide rotation range to allow for perfect alignment, and a mounting bracket lock for tamper resistance. A dust cover keeps the unit clean during construction. It comes with a 10-year limited warranty.