Deter nuisance barking with a decorative touch. When the Outdoor Bark Control is within range of constant barking, an internal microphone picks up the sound and the unit is activated. The unit emits an ultrasonic sound. The sound can only be heard by the dog. Startled by the high-pitched sound, the dog should stop barking, as it will associate its bark with this unpleasant noise. The Outdoor Bark Control has 4 settings including 3 sensitivity levels and a test mode and is effective up to 50 feet. NOn-returnable 3 days after receipt.