HARDWIRED -- First Alert #SC9120B smoke and carbon monoxide alarm. Features a carbon monoxide sensor, dual ionization smoke sensor, and separate visual and audible smoke and carbon monoxide indication to eliminate confusion. Intelligent Sensing Technology for fewer nuisance alarms, smart 3-wire interconnect, and Quick-Connect wiring harness for connection to AC (alternating current) power. Also includes an 85dB horn and 9-volt battery backup. Battery life varies according to use and application. 2 silence features: Can silence the low battery chirp for up to 8 hours or temporarily silence an unwanted alarm. Latching alarm indicator. Interconnectable with up to 18 devices. 120V AC/DC. 10-year limited warranty. UL (Underwriter's Laboratories) listed.