Small yet effective, the Kidde i9050 Battery Powered Smoke Alarm keeps your family from harm through a horn-style alert when smoke or fire threatens your home. This device is powered by a standard 9V battery and works even when the electricity is out. The Kiddie i9050 Battery Powered Smoke Alarm features a red power indicator to let you know its on and ready, a test button for family fire drills or to assure Mom and Dad the unit is working properly, a low battery indicator to let you know that your 9V needs replacing, and a tamper resist feature to assure that little hands dont accidently disable the device. Simple installation with no wiring required. 5 in diameter. This unit may be wall or ceiling mounted.