First Alert Bark Genie Automatic Ultrasonic Bark Deterrent Bark deterrent device automatically detects barking and reacts by emitting an ultrasonic sound that only dogs can hear; stands alone, hangs on a tree, or can be mounted on a wall An ideal solution for dogs who bark continually throughout the day or night, when their owners are away, when visitors are over, or when people or other animals walk by Detects barking up to 50 feet away Pet-friendly ultrasonic technology is safe and effective; provides 3 adjustable levels of sensitivity Works with all dog breeds