Dog Training and Behavior Aid: Using the latest ultrasonic technology, the anti-barking device automatically emits a high-pitched tone that only dogs can hear. Automatically senses the sound of a dog, and once the dog stops barking, the ultrasonic barking controller automatically stops emitting ultrasonic waves. Bark Control for All Sizes and Breeds: Bark control device available in 4 sensitivities. You can set the most suitable gear according to the environment, select the sensing distance, and adjust the sensitivity to achieve this. Level 1 is the least sensitive and Level 4 is the most sensitive. Safe for Dogs and Humans: The dog barking control device has no electric shock, no pungent smell, no beeps, safe for pets and harmless to humans, the anti-barking device automatically emits ultrasonic waves to stop dogs from barking when you Great for letting you go when you're away from your dog. Keep the dog quiet, creating a peaceful environment for your family and neighbors. If the dog is hearing-impaired or aggressive, the device may not work as expected. USB Rechargeable Dog Barking Control Device: Rechargeable anti-barking device with indicator light for easy use. A 5-hour charge gives you 30 days of use, saving you endless hassle and battery investment. No need to install batteries, it works right out of the box. (It is recommended to fully charge before use, the effect will be better) No Dog Barking Indoor and Outdoor: Tested, the anti-barking device works best within 32 feet, which completely frees your hands compared to traditional dog training devices. You can easily train your dog's behavior by turning the knob. Great for stopping neighbor and homeless dogs from barking outdoors.