Details: Simply place the alarm behind any door. If an intruder attempts to open the door, the wedge-shaped design will prevent it from opening and activate a 120 dB alarm. The alarm will scare off the would-be intruder and alert you to the attempted entry. An adjustable sensitivity switch prevents tampering. When traveling, just toss this lightweight unit in your luggage. The on off switch will prevent the unit from accidentally sounding. Requires one 9 volt battery – not included