100% HARMLESSHIGH TECH：The ultrasonic frequency is 100% safeharmless to your pet dogs and completely inaudible to human ears. When the Outdoor Bark Control is within a range of barking dog,the internal microphone picks up the sound and it will be automatically activated.The Outdoor Bark Control will emit an ultrasonic sound to deter unwanted barking. NEW DESIGN:Our Outdoor Anti-Bark Controller is designed like a cute small birdhouse.You can easily hang or mount on a fence,wall or tree with a landyard to keep you dog from barking.Suitable for most types of pets. DURABLEWATERPROOF:Especially design for outdoor use.Our Ultrasonic Outdoor Anti-Bark Controller is made of ABS plastic,durablewaterproof.So you don't worry about the rainy day. HIGH FUNCTION DOG BARK DETERRENT:It is effective range 50 feet.And there are 3 range levels and a test mode,you can use the test mode to verify the microphone and speaker are working properly.The two color LED indicator show good or low battery. HOW TO WORK :The dog bark deterrent emits an ultrasonic sound. Humans will not be able to hear this tone, but it can be easily heard by dogs. Startled by the high-pitched sound, which is safe and effective for dogs of all sizes and breeds, the dogs barking will be deterred. Dogs will soon associate their barking with the unpleasant tone, and will remain quiet to avoid the sound. When the dog stops barking, the ultrasonic sound also stops.