Safe & Friendly Dog Barking Silencer: The anti barking device for dogs will not disturb or harm people or dogs. It works by emitting ultrasonic that only dogs can hear to make the dog stop its annoying barking. So rest assured that dog barking deterrent device are not harmful to human or dog. Auto Anti Barking Device: Our barking control devices is used to prevent excessive dog barking. Using the latest ultrasonic technology, the anti barking device only works when it senses dog barking. Dog bark deterrent devices will automatically stop excessive, noisy dog barking and give you a quiet life! 4 Modes Barking Control Devices: This anti barking device has 4 adjustable ultrasonic levels (Test, Low, Medium, High), provide a wide range of ultrasonic to stop dog barking: 12-50 FT. The dog barking control device effectively stop barking indoors and outdoors. You can turn the knob to test different mode for best results. Waterproof Anti Barking Device: Our anti barking device for dogs indoor and outdoor is waterproof, so dog barking silencer can be used even in rainy days. The barking control device can be easily hung from a tree, fence post or anywhere with the included lanyard, which can effectively stop dog barking. Fits For Most Dogs: This anti barking device works for most dogs, but doesn't work for dogs that are deaf or hearing impaired. If the dog does not stop barking when you first start using anti barking device, please allow 2 weeks for the dog to adjust.