120V SMK ALARM W BATT PHOTO Help keep your family safe with this hardwired smoke alarm that interconnects with other First Alert enabled alarms to create a home safety network Alarm features photoelectric smoke-sensing technology that detects smoke while minimizing false alarms; Optipath 36�patented technology provides 360 degrees of access to the smoke alarm Loud 85-decibel siren sounds to alert you to danger; intuitive latching alarm indicator identifies which unit triggered the alarm Hardwired alarm includes 9V backup battery for continued monitoring in the event of a power outage Includes single test/silence button and low-battery warning 10-Year limited warranty First Alert Hardwired 120-Volt Smoke Alarm with Battery Back-Up