This is a 2 in 1 Personal/Door Alarm. It acts as a burglar alarm and a personal alarm. Hang it on any doorknob (non-metallic doors), and it instantly and automatically sounds when an intruder touches the doorknob.

Also, Use As A Personal Alarm

Carry it with you and just pull out the metal chain to sound the alarm and deter an assailant. The alarm is 120 decibels. Requires one 9-volt battery.