BRK, , Hardwired Photoelectric Ionization, Battery Back Up, Double Protection For Both Flaming Smoldering Fires, Dual Photoelectric Ionization Smoke Sensing Technologies, Includes 2 Latching Features, 1 Alarm Latch Easily Identifies An Initiating Alarm Even After Alarm Condition Has Subsided, Second Is A Low Battery Latch That Identifies Which Unit Is In Low Battery Condition By Blinking The Green Power Light, Has 2 Silence Features That Includes A Low Battery Silence That Temporarily Silences The Low Battery Chirp For Up To 8 Hours, Includes An 85 Db Horn, Single Button TestSilence, An Easy Access Battery Drawer Dust Cover, Installation Is Quick, Easy Cost Effective, Connection To AC Power Is Made With A Quick Connect Wiring Harness