Introducing the revolutionary BRK 9120 series smoke alarms which 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 you 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 AC-powered smoke alarm with battery backup includes these features: ionization sensor which helps detect fast flaming fires that consume combustible materials rapidly. 120-Volt AC inter-connectable (with maximum 18 compatible devices). the alarm can 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. Latching alarm indicator which automatically identifies which unit initiated the alarm. Smart technology to reduce nuisance alarms. 9-Volt battery backup for peace of mind during power malfunction. Single test/silence button which both silences a non-threatening alarm or low battery warning and allows you to test the unit's functionality. 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. Mounting bracket lock for tamper resistance. Dust cover to keep unit clean during construction. 10-Year limited. 6 pack of hardwired smoke alarms, includes battery backup for power outages Tamper resistant locking pins, single button silence/test and loud 85Db alarm 120-Volt AC power with 9-volt battery backup (included) to keep alarm functioning during power outage Open mounting design for easy installation with side load battery compartment for quick replacement and interconnect able up to 18 units (12 smoke, 6 co/heat/relay) 10-Year limited Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in home safety