Stops your dog's constant barking almost like magic. Barking activates the unit to emit a two-second ultrasonic sound that can only be heard by your dog. Startled, your dog will soon associate this unpleasant sound with his behavior and stop the unwanted barking.Unobtrusive table-top unit for indoor use.No collar needed.Creates a bark-free zone for one or more dogs.Device emits loud ultrasonic tone that only dogs can hear.Activated by dog's bark or manually by the owner.Operates on 9-volt battery which will last six months or 2,000 activations.Low battery light flashes to indicate low battery..