Automatic Dog Bark StopperThe device intelligently captures dog barking from up to 15 meters away, and automatically emits an ultrasonic sound that distracts your dog to stop unwanted barking, allowing you to enjoy the 'a moment of peace and silence. Dog Barking StopperUltrasonic 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 expected. It is not recommended to use one device against two or more dogs barking at the same time. 3 Levels of OperationAdjustable frequency dog barking deterrent device is suitable for different dogs. 15KHZ-30KHZ is suitable for big vicious dogs. 20KHZ Suitable for soft dogs. 30KHZ Suitable for small dogs. It is recommended for dogs aged 6 months to 8 years old. USB RechargeableThe ultrasonic dog repellent builds in a rechargeable lithium battery, the device can work continuously for 30 days after being fully charged in 5 hours. Red/blue color indicates battery status. Easy Installation And WaterproofThe dog bark stopper can be hung on a tree, wall or fence to prevent your own dog or your neighbors barking. Make sure the bark controller is facing the dog within easy reach without any obstructions.