Ultrasonic outdoor bark control unit looks like an ordinary birdhouse that can hang in a tree, on a fence post, or anywhere outside. It can detect barking up to 50-feet away and has 3 range settings. Whenever a dog barks nearby, he/she will hear a safe, high-pitched sound (audible to humans) that will teach him to stop the annoying habit. Includes a test mode. Durable and weather proof. Low-color LED (light emitting diode) for good/low-battery indication. Requires (1) 9-volt alkaline battery, not included.