Upgraded Version Ultrasonic anti-bark devices automatically detect barking from as far away as 50 feet. The barking control device automatically emits high-pitched sounds that only dogs can hear. Once the dog stops barking, the ultrasonic bark control automatically stops emitting ultrasonic sounds. 100% Safe & Friendly for Animals and People Our bark control devices emit ultrasonic waves to make dogs stop barking, harmless to dog health. It's also safe for other pets, your family and neighbor. Multiple functional modes Four levels of operation including a test mode. Test-used to verify the microphone and speaker are functional. Range Up to 50 Feet Sonic Anti-Barking Ultrasonic frequencies are harmless to pets and completely inaudible to the human ear, so you can use this device safely. Outdoor sonic bark silencer can be hung on a tree, indoor, outdoor wall or fence post to stop dogs barking. Make sure the ultrasonic bark house be placed facing the dog and within range of the dog up to 50 feet away. Universal Fit for Any sizes(breeds) of Dogs The ultrasonic bark controller uses high-frequency sound that works to reduce excessive bark of dogs within hearing range; suitable for dogs 6 months and older up to 50 feet range. NOTE: Does not work on deaf or hearing impaired dogs.