Automatic Dog Bark Control: The device intelligently captures dog barks up to 15 meters away, and automatically emits an ultrasonic sound that distracts your dog to stop unwanted barking, allowing you to enjoy a moment of peace and quiet. Dog Bark Stopper: The ultrasonic frequencies are harmless to pets and completely inaudible to the human ear. If the dog is hard of hearing or aggressive, the device may not work as intended. It is not recommended to use one device against two or more barking dogs at the same time. 3 Operation Levels: The dog bark deterrent device with adjustable frequency is suitable for different dogs. 15KHZ-30KHZ is suitable for large and vicious dogs. 20KHZ is suitable for gentle dogs. 30KHZ is suitable for small dogs. It is recommended for dogs aged 6 months to 8 years. USB Rechargeable: The ultrasonic dog repeller has a built-in rechargeable lithium battery, the device can work continuously for 30 days after being fully charged in 5 hours. The red/blue color indicates the battery status. Easy Installation & Waterproof: The dog bark control device can be hung on a tree, wall, or fence to prevent your own or your neighbor's dog from barking. Make sure the bark controller is facing the dog within reach without any obstruction.