Description: 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. Operation: 1) This alarm is operated by a 9v battery (Not included) 2) Open the battery door on the back side of the alarm unit, and place a 9v battery in the battery compartment, Make sure the battery is installed correctly before use. 3) After installing 9V battery, place the doorstop alarm behind a closed door to secure the room 4) If the secured door is opened, the edge of the door will press down on the wedge plate of doorstop alarm and set off the alarm, which will sound at 120dB siren continuously. 5) The sensitivity of the vibration sensor can be adjusted from low to high as indicated in order to meet your needs. 6) When the siren starts to sound weak, it is time to change the 9v battery as described in step 2 7) Turn the power switch off when the doorstop alarm is not in use. The alarm unit can be used as a door stop to prevent the doorknob from hitting the wall if the hinged door is opened too roughly.