The Door Guard Alarm is a very versatile vibration alarm. Ideal for home, office, or travel. This alarm requires no installation, simply hang it on any doorknob and it instantly detects any vibration. When the alarm is tripped, it will emit a 98 dB alarm for 20-30 seconds, then will reset in 3-5 seconds. The sensitivity of the alarm is easily adjusted with a screwdriver. The Door Guard can also be used as a flashlight. Uses 2 AAA batteries (not included).