Model USI-3204 Smoke and Fire Alarm 120 Volt AC Powered. Convenient pull-out drawer for easy battery replacement. Battery Pull-Tab activates battery and reduces installation time. 9V Battery Back-up in Event of AC power failure. Super heavy duty battery included. Full dust and contaminant cover protects the smoke alarm spray applications, thereby eliminating the need to remove the alarm during home construction. Silencer Feature, convenient silencer button with automatic reset allows you to temporarily override alarm ideal for cooking smoke and fireplaces. Eliminates nuisance alarms. Ideal for replacement of most existing smoke alarms. Interconnectable up to 18 units 12 smoke alarms maximum/ 6 CO alarms . When unit goes into alarm, all interconnected units sound their alarm. When smoke is detected, the red LED flashes on the initiating smoke alarm. Green LED Indicator for AC power. Separate large size mounting plate attaches to any standard rectangular or octagon junction box and covers drywall cutout. Loud 85 Decibel Horn. Low Battery Audible Indicator test button. 120 VAC 60 Hz power. Wire harness for easy connection.