Suitable for all breeds and sizes of dogs, it can effectively prevent your dog or your neighbors from barking for 39 seconds, preventing dogs from barking at a certain time, and the ultrasonic bark controller has a 25 feet effective distance. Outdoor ultrasonic bark control with 3 adjustable ultrasonic range levels and test modes: low range, mid range, high range, test mode (checks microphone functionality and speaker). Ultrasonic frequencies are harmless to pets and completely inaudible to human ears. It provides a safe and effective training tool for your dog or your neighbor The new bark controller features a well-designed mini shape that is easy to place and hide. The two-color LED indicates whether the device is powered on. When the external bark control is within range of the dog's bark, the microphone picks up the sound and automatically activates the device. The external tamper evident controller emits ultrasonic waves. (Ultrasonic noise may come from dogs, but is muted for humans)