Universal Security Instruments MP117 Photoelectric Smoke Alarm is perfect for new or replacement installations - 120-volt AC/DC hardwired photoelectric smoke alarm offers timesaving installation features value and quality - choose this alarm if you are looking for a photoelectric alarm with superior nuisance alarm resistance. Photoelectric smoke alarms are typically more effective at detecting slow smoldering fires, which burn for hours before bursting into flame. Interconnect able up to 24 compatible devices - when one alarm activates, interconnected alarms sound throughout the home, providing additional time to escape safely. A product end-of-service life warning sounds when it is time to replace alarm. for added security, tamper-resistant locking feature prevents unwanted battery or alarm removal. Replace battery without removing alarm from bracket. 9-volt alkaline battery (included) continues protection in the event of a power outage. The patented Quick Find alarm location feature easily identifies first alarm to sound in an interconnected system. The Auto sensitivity calibration feature prevents nuisance alarms and provides consistency in alarm sensitivity. The self-diagnostics feature performs a status check upon power up to ensure the alarm is functioning properly. The ambient condition compensation feature automatically adjusts sensitivity for temperature and humidity conditions. The quick connect wiring harness features longer 8-Inch pigtail wires, pre-stripped for convenient installation. The larger mounting base covers drywall imperfections and old paint marks. The single silence/test button temporarily quiets nonemergency alarms and tests alarm functionality. The full-size plastic dust cover protects the alarm from dust, debris and painting during construction or home remodeling. MEETS INDUSTRY STANDARDS: Listed to UL Standard 217 and California State Fire Marshal approved. 10-year limited warranty. MP117 is 120 Volt AC/DC Hardwired Smart Alarm.