【Automatic anti-barking for dogs】The device intelligently detects your dog's barking up to 15 meters away and automatically emits an ultrasonic sound that distracts it to prevent it from barking, allowing you to enjoy a moment of peace and quiet. 【Anti-barking for dogs】The ultrasonic frequencies are harmless to animals and completely inaudible to the human ear. If the dog has impaired hearing or is aggressive, the device may not work properly. It is not recommended to use the same device against two or more dogs barking at the same time. 【3 function levels】This anti-barking device with adjustable frequency is suitable for different types of dogs. The frequency 15 kHz to 30 kHz is suitable for large aggressive dogs. The frequency 20 kHz is suitable for mild dogs. The frequency 30 kHz is suitable for small dogs. It is recommended for dogs aged 6 months to 8 years. 【USB rechargeable】This ultrasonic dog repeller has a built-in rechargeable lithium battery, which can work continuously for 30 days after a full charge of 5 hours. Red/blue color indicates battery status. 【Easy installation and waterproof】This anti-barking device can be hung on a tree, a wall or a fence to prevent your dog or your neighbor's dog from barking. Make sure the anti-barking device is facing the dog within range, without any obstacles.