The Elite Outdoor Ultrasonic Bark Control gives you peace and quiet in your own backyard. Whenever a dog barks within range of the device, the dog will hear a high-pitched sound that most humans can't hear. While ultrasonic sound is harmless, it is teaches the dog to stop barking. You can set the digital timer to turn the unit on and off at specific times, just like an alarm clock. The outdoor bark control unit is disguised as a birdhouse so you can hang in a tree, on a fence post, or anywhere outside in your yard. It has a range of up to 50 feet and a single unit could cover a 1/4 acre yard. Add more units to cover a larger property.