Designed to draw attention to any crisis, our 130db Personal Alarm is as loud as eight 100-decibel alarms. The alarm is activated when the strap attached to the alarm pin is pulled. Travels easily on your belt or in your purse. The Door Alarm accessory converts the Personal Alarm into a portable door or window alarm. Great for home, hotel rooms, college dorms, etc. Requires one 9 volt battery.