Designed for outdoor, it will train your dog (or the neighbor’s ) not to bark . Safe and effective for all sizes and breeds of dogs. When the Outdoor Bark Control is in the field of a dog barking , an internal microphone detects the sound of barking and automatically activates the system. The Outdoor Bark Control emits an ultrasonic perceived by dogs but not humans. Surprised by ultrasound, the dog should stop barking as it will associate its bark with this unpleasant noise for him . When the dog stops barking , the Outdoor Bark Control stops also .