The SUPER DOOR STOP ALARM is a combination of door stop and entry alarm. When someone attempts to open the door, it presses down on the door stop and a 120 decibel alarm sounds. The alarm is silenced when pressure is removed from the unit. There is also a tamper resistance feature that utilizes as movement sensor that will activate the alarm if it is tampered with. The unit includes a low battery light and uses one 9 volt battery (not included).