UPGRADED DOG TRAINING AND BEHAVIOR AID: Using the latest ultrasonic technology, the anti-barking device will automatically emit a high-frequency tone that only dogs can hear. Automatically senses the dog's sound, when the dog stops barking, the ultrasonic bark control automatically stops emitting ultrasonic waves. ANTI-BARKING FOR ALL SIZES AND BREEDS: The anti-barking device has a choice of 4 sensitivity levels. The environment can be set with the most suitable gear, the induction distance can be selected, adjust the sensitivity to achieve. Level 1 is the least sensitive and level 4 is the most sensitive. SAFE FOR DOGS AND HUMANS: Dog bark control devices without electric shock, no irritating odor and no beeping, safe for pets and harmless to humans, the anti-barking device will automatically send out ultrasonic waves to stop the dog from barking, perfect for letting you go when you leave your dog. The dog stays quiet and creates a calm environment for you, your family and your neighbors. If the dog is hearing impaired or aggressive, the device may not work as intended. USB RECHARGEABLE DOG BARK CONTROL DEVICES: Rechargeable anti-barking device with indicator light can be used effortlessly. 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. STOP DOG BARKING INDOORS OUTDOORS: Anti-barking device tested to get the best results within 32 feet, it completely frees your hands compared to traditional dog trainers. You can easily train your dog's behavior by turning the dial. Excellent for stopping neighbors and stray dogs from barking outdoors.