Alarm plugs into any standard 120V AC outlet with no additional mounting and battery operated alarm backup provides consistent protection for added safety during power outages. Mute button mutes unnecessary alarms and tests alarm function with same button. EZ access battery door has a front-open compartment that allows easy battery change without dismounting alarm. Low battery signal mute quiets low battery signal for up to 8 hours. 2 ''AA'' batteries included. Loud 85dB alarm. 5 year limited warranty.