This personal alarm combines two great deterrents to attack- a 130 dB alarm and flashing light. It looks like an ordinary pager and attaches to a belt or purse for easy accessibility. There are many different ways this alarm can be used a personal alarm or a purse or briefcase or backpack alarm. Using the included door clip you can use this item as a Door-window alarm. With the included door clip you can also use this item to protect your laptop computer from being stolen. As an added deterrent an alarm warning decal is included. Unit operates on one 9 volt battery (not included). Measurements are 3 inches x 2 inches x 1 inch.