This wireless magnetic break alarm attaches to glass surfaces and emits a high pitched sound for 30 seconds if the glass is broken. The alarm automatically re-sets after the 30 second alarm terminates. The Glass Break Alarm is ideal for detecting breakage on home, office or RV windows, glass doors, skylights, etc. It is easily installed with a peel and stick adhesive. The alarm operates off a 9-volt button cell battery (included). Has On/Off Switch. One-year limited warranty. Three per package.