Universal Security Instruments Hardwired Photoelectric Smoke and Fire Alarm with Battery Backup, Model MP117 Photoelectric Smoke and Fire Alarm responds quickly to slow-smoldering fires for optimal protection Fully interconnectable with up to twenty-four USI-compatible devices Features a quick activation pull-tab and a front-loading battery drawer for replacement without removing the alarm from the bracket Suitable for houses, apartments, and mobile homes Comes with a ten-year limited warranty