HARDWIRED SMOKE DETECTOR - Hardwired interconnected smoke alarm, can connect up to 12 alarms. It is more precise and stable than wireless interconnection..INTERCONNECTION TEST - If the fire detectors are interconnected, you only need to press one test button during the weekly test, and the rest can be tested at the same time..9V BATTERY BACKUP - The fire alarm is powered by a 120V power and a 9V backup battery. The alarm battary will last for at least 1 year, providing protection in the event of a power outage..SILENCE MODE - Worried about false positives? The smoke detector has a silence button, you can hold it down for five seconds to calm it..SIZE & CAPABILITY - 5” diameter x 1.6” depth, UL217 certified. Home fires start every 83 seconds, the fire detector can quickly identify the fire and allow the family to flee quickly.