First Alert, Wireless Smoke Alarm, Interconnected Fire Alarm System, Wireless Technology Allows The Detectors To Connect With Other Compatible Wireless Enabled Alarms In Your Home To Create A Wireless Safety Network, An 85 Decibel Siren As Well As A Voice Alarm Will Sound To Let You Know Where The Danger Is, Detectors Photoelectric Smoke Sensors Are Each Designed To Reduce False Alarms From Cooking Smoke Or Shower Steam While Remaining Sensitive To Real Danger, Single Button To Silence False Alarms & Test The Unit, Uses 2 "AA" Batteries, Not Included.