This unit is Photoelectric smoke and Carbon Monoxide detector, it is also Wireless with a battery Backup. If you need to tie this into other Hardwired units you will need to get the SA521CN(SA520B) to use as a bridge unit. First Alert Onelink allows wireless smoke detector integration with battery backup. 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. 7-year limited warranty. Meets UL standards.