First Alert Onelink allows wireless smoke detector integration. 120VAC hardwired wireless detectors interconnect alarms with battery backup. Expand protection to include existing hardwired detectors and new wireless detectors by replacing one existing hardwired alarm with Onelink. By adding Onelink battery operated alarms elsewhere, when one alarm sounds in either series of alarms, all alarms will be notified. Easily link alarms together with the press of a button. Photoelectric smoke sensor reduces nuisance alarms from cooking smoke or shower steam. Easy access battery drawer: no need to remove alarm from ceiling to change battery. 10-year limited warranty. Meets UL standards.