The Motorola BARK500U Shock-Free No-Bark Ball is an indoor ultrasonic bark deterrent that helps you control your dog's barking patterns in key areas of your home. The BARK500U detects your dog's bark and allows him to bark freely for 5 seconds, then delivers a pulse of ultrasonic sound. This high frequency sound is specially designed to be an annoyance to animals, while above a human's range of hearing. The BARK500U can be mounted on a wall or manually operated for other problem behaviors and the magnetic base allows you to easily adjust the direction of the ultrasonic sound.