Feature: Pet friendly anti-barking device: this ultrasonic barking control device works by sending a stable frequency sound that only dogs can hear, preventing dogs from barking and calming dogs. No irritating smell, no electric shock, anti-barking for dogs that only work when dogs bark. Bark repellent device is harmless to the hearing of people and dogs, perfect to create a quiet department for dog lovers and stop unwanted behaviour. Effective for dogs of all sizes: the ultrasonic dog barking repellent with 3 adjustable sensitivity and frequency levels (15-30 kHz for large, naughty dogs); 20 kHz for educational dogs; 30 kHz for small dogs) prevent dogs of different sizes from barking easily. Adjusting the frequency for each week can maintain the training effect. Easy to use: this rechargeable dog bark control device with LED indicator can be used effortlessly. When you work on 3 different levels, the light flashes blue every 6 seconds; red light stays on for 3 seconds when the sound barking is triggered; the red light flashes at low power. Outdoor and indoor use: the human bark devices with IPX4 rain protection function and the portable hook can be easily hung up trees, walls or fence posts. But when heavy rains, it's best to bring it back to extend its lifespan. The ultrasonic dog device can be placed on a desk, wall and shelf with a height of more than 1.5 m, which can be adjusted more effectively for barking, digging, fighting, etc. Material:ABS