Kidde i12040 Hardwire Smoke Alarm with Hush Feature and Battery Backup, Alkaline Battery Hush feature temporally silences nuisance alarms One touch test button tests units electronic circuitry Battery backup provides continuous protection even during power outages, 9-Volt battery included Tamper resist locking pin helps deter alarm tampering and theft Kidde&#8217;s smoke alarms meet the requirements of Underwriters Laboratories (UL), an independent facility that tests products for compliance with widely-accepted safety standards