At only 2.5 inches long this window alarm inconspicuously protects your home from intruders. This unit uses a magnetic sensor to detect the opening of a protected window. A 105 dB alarm will then alert you to an attempted entry and scare off potential intruders. The owner may open the window or other protected object without setting off the alarm by inserting a deactivation key. Once the deactivation key has been removed and the protected door or window is opened the alarm will sound until the key is inserted or the door or window is closed. May also be used within the home to alert parents to children opening a gun or medicine cabinet or used to protect exterior doors particularly those hard to protect sliding glass doors. Commercial uses include showcases and cash registers. Dimensions are 2 and one-half inches by 1 and one-half inches by one-half inches. The deactivation key adds one-half inches to the height (3 inches with key inserted). Batteries included.At only 2.5 inches long this window alarm inconspicuously protects your home from intruders. This unit uses a magnetic sensor to detect the opening of a protected window. A 105 dB alarm will then alert you to an attempted entry and scare off potential intruders. The owner may open the window or other protected object without setting off the alarm by inserting a deactivation key. Once the deactivation key has been removed and the protected door or window is opened the alarm will sound until the key is inserted or the door or window is closed. May also be used within the home to alert parents to children opening a gun or medicine cabinet or used to protect exterior doors particularly those hard to protect sliding glass doors. Commercial uses include showcases and cash registers. Dimensions are 2 and one-half inches by 1 and one-half inches by one-half inches. The deactivation key adds one-half inches to the height (3 inches with key inserted). Batteries included.