Automatic Dog Barking Control The device intelligently captures barking dogs up to 15 feet away and automatically emits an ultrasonic sound that distracts your dog to stop unwanted barking, so you can enjoy a moment of peace and silence. Dog Bark Stopper 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 expected. It is not recommended to use one device against two or more barking dogs at the same time. 3 Levels of Operation The adjustable frequency bark deterrent is suitable for different dogs. 15KHZ-30KHZ is suitable for big bad dogs. 20KHZ Suitable for gentle dogs. 30KHZ Suitable for small dogs. It is recommended for dogs aged 6 months to 8 years. USB Rechargeable The ultrasonic dog repeller builds in a rechargeable lithium battery, the device can work continuously for 30 days after being fully charged within 5 hours. The red/blue color indicates the battery status. Easy installation and waterproof The anti bark dog device 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.