Ultrasonic design: Based on the theory that a dog trainer can effectively train your dog to be obedient and prevent bad behaviors such as barking, digging, and chewing. In addition, they are harmless to humans and pets, and the sound can only be heard by pets. Easy to use: Open the battery cover first, and then insert the 9V battery (not included). Only pets can hear the sound. Finally, turn on the switch and it can do its magic. If necessary, it can also be used as a flashlight. LED flashlight and battery indicator: The super bright LED flashlight function is very helpful when walking or jogging at night, and can also be used as a battery indicator. Portable and comfortable: Ultrasonic dog barking prevention measures approx. 12.5 x 4 x 2.5 cm (length x width x height), it can be easily put in a pocket. Ultrasonic dog bark prevention has a lanyard, which allows you to insert a dog bark control stop device wherever you need it, such as jogging or cycling, hiking, parking, etc.