The Wired-In Kidde Combination Carbon Monoxide & Smoke Alarm is an interconnected alarm that provides two important safety devices in a single unit. The 21006377 combination alarm includes a voice warning system that announces "Fire, Carbon Monoxide or Low Battery". The voice alarm eliminates any confusion and clearly warns you and your family of a smoke or carbon monoxide danger. This AC/DC operated technically advanced combination alarm provides protection even during a power outage when most incidences occur.