First Alert Onelink combination smoke and carbon monoxide alarms. Create wireless links with other smoke alarms and carbon monoxide alarms. Talking alarm can be easily programmed for alarm's location within the home (11 pre-programmed choices). Voice also notifies which hazard is being sensed. Easily link alarms together with the press of a button. When one alarm sounds, they all sound for maximum whole home protection. Photoelectric smoke sensor reduces nuisance alarms from normal smoke or steam. Easy access to battery drawer: no need to take down alarm to change battery. 5-year limited warranty. Meets UL standards.