Safe and Friendly for Animals and People: This dog silencer ultrasonic bark stopper has been tested and proven to be completely harmless to human animals and plants. Due to its precise sonic frequency, you may not even hear it! It can take up to 2 weeks for the barker to "learn" what the piercing noise means. Effective Range Up to 50 Feet: Our outdoor dog barking control device is conveniently designed with multiple settings; multi-directional microphone picks up dogs in any direction! Mode 1: Low range (up to 15 feet); Mode 2: Medium range (up to 30 feet); farther? Mode 3: High Range (stops all dogs within 50 feet). Easy to use: The dog bark stopper has a built-in pickup that detects dog barking within 50 feet and automatically emits ultrasonic waves that dogs can hear. Once the dog stops barking, the device will automatically stop. Compared with traditional dog training equipment, it completely frees your hands. Automatically and effectively train your dog to stop excessive and noisy barking. Waterproof: The dog barking control device has IPX4 waterproof rating, and the outer shell is UV-resistant and not easy to fade. Designed to easily hang/mount on trees, walls or fence posts to stop any dogs from barking (within range), indoors, outdoors, etc. Everywhere. This dog deterrent is not suitable for aggressive dogs and dogs with hearing loss. Energy Saving: Uses 9-volt battery (not included), average battery life is 5-6 months, depending on usage. Can be started with a 9V battery (not included). Hold it at arm's length and whistle into the microphone. The device will beep and the LED will flash green.