NePets Ultrasonic Outdoor Dog Bark Control, Dog Barking Control Device, Anti Bark Birdhouse Deterrents with Bird House Design For Outdoor Use Only Uses ultrasonic sound to deter unwanted barking Detects barks up to 50 feet with the use of an internal microphone 4 Levels of operation including a test mode One year Limited Warranty .The product is protected by national patent law,With CE & ROHS certificate. Note: If the dog is deaf or hearing impaired, he may not react to the Outdoor Bark Control.