This dog anti-barking controller has a sensitive microphone inside to isolates and picks up barking and then emits harmless high-pitched ultrasonic sound which can be heard by dogs only to deter the excessive disturbing bark from your dogs. The dog bark controller is effective with a range of 50 feet,detects dog barks up to 50 feet with 4 levels of operation including a test mode.，a safe and effective stuff to train your dog. The ultrasonic frequency is inaudible to human no harm to your family and pets completely which is totally safe to use. Water droplet shape design, simple and chic which is also easy to install in the house to stop your dogs' excessive barking. 100% Satisfaction Guarantee,any problem, please do not hesitate to contact us and we will solve the problem for you 24/7.