The highly effective Exit Stopper can serve as an inexpensive security device and help stop theft by alerting you to any unauthorized exits or entries through emergency exit doors. How it works: If the protected door is opened, the electronic Exit Stopper emits an ear piercing alarm for 30 seconds, 3 minutes or continuously (as preset by the user). A key operated override will silence the alarm and allow authorized exits. The unit can be set for a 30 second delay before arming or tripping. Exit Stopper “Always Active” allows the key holder to reset the alarm, but does not allow the alarm to be turned off. Exit Stopper is fitted with a 9 VDC alkaline battery. It is available in red or green for almost any type of door, mounting or installation, including remote placement of the alarm (not for outdoor use).