The Doberman Burglar Window Alarm is a sleekly designed unit enabling it to function with many sliding glass windows. This product protects the entry of potential burglars via its window vibration detection. When an intruder is attemption to break-in and the window vibrates more than normal or is broken, the vibration sensor triggers the alarm. Printed on the reverse side of this product is a red warning label that can be seen outside through the window.