First Alert SA521CN-3ST

First Alert Wireless Interconnect photoelectric smoke alarms link the alarms throughout your home. 120 V AC hardwired wireless detectors with battery backup integrate single alarms into a system. Expand protection by replacing one existing hardwired alarm with Wireless Interconnect and linking to existing hardwired and battery operated alarms. By adding Wireless Interconnect battery operated alarms elsewhere, when one alarm sounds, all alarms will be notified. Photoelectric smoke sensor reduces nuisance alarms. Easy access battery drawer: no need to remove an alarm from the ceiling to change battery. Includes 10-year limited warranty. Meets UL standards.