Features a photoelectric patented smoke entry system, mute/silence button, end of life signal, power LED (light emitting diode) and alarm indicator. Slim design with nuisance free technology and half the size of a standard alarm. Wall or ceiling mount with easy slide mounting bracket. 85 decibel alarm. 9 volt battery included. 10-year limited warranty. UL (Underwriter’s Laboratories) listed. No. P900: Power Source: Battery Operated, Voltage: 9V, Sensor Type: Photoelectric, Dimensions: 4.92 In. W. x 0.94 In. H. x 4.92 In. L., Battery Back-up: Battery Only, Alarm Type: Smoke, Decibel Level: 85dB, Battery Type: 9V Battery, Batteries Included: Yes, Color: White, UL Listed: Yes, Warranty: 10-Year Limited, Pkg Qty: 1, Package Type: Clamshell