The Audible Alarm Activates When The Remote Wireless Monitor Detects A Water Hazard Or Detects The Temperature Falling Below 45 Degrees F. The Audible Alarm Functions Up To 120-Feet (It Could Even Be Left With Neighbor) From The Monitoring Device And Operates Continuously For 24-Hours On Fully Charged Batteries. Multiple Audible Alarm And Flasher (Item No.EBPR-17-THP203) Detectors Can Be Linked To Monitor Multiple Locations In The Dwelling. FCC Approved. Requires One 9-Volt and Three AAA Batteries (Not Included).