[Working principle] - When the product microphone detects a dog barking, the product automatically emits a high-pitched ultrasonic wave. This ultrasonic wave cannot be heard by human ears but can be heard by dogs. For dogs, it is a harsh noise, so the dog will stop barking and go away. 【Product Design】-- The product is designed for outdoor use. The appearance is designed as a bird house. It can be easily hung on a tree, anywhere in the house or in your garden. It can be hung or placed on a table at will or anywhere else. [Product Features] - The product can prevent excessive dog barking from affecting you and your neighbors. The outdoor ultrasonic anti-bark stopper can effectively prevent the dog from barking and does not require a receiving collar. Safe and effective, suitable for dogs of all breeds and sizes. [Precautions] - Ultrasound only allows the dog to hear what makes him uncomfortable, and there is no has no substantial punishment. The dog will adapt to the product after