Fund Anti Bark Control Device Indoor Outdoor Ultrasonic Deterrent Bark Stopper Birdhouse for Dog Pets Best Trainer 1.Birdhouse Shape Out door Bark Controller Uses ultrasonic technology to stop barks; 2.Sensitive microphone isolates and picks up barking up to 50 feet away to stop barking both outdoors and indoors; 3.Effective on most dogs within range (some dogs may not be responsive to ultrasonic correction) 4.Four adjustable ultrasonic volume levels?- test, low, medium, and high, with LED battery power level indicator 5.Safe: human can't hear the ultrasonic sound and it will associate the bark with unpleasant noise,when the dog stops barking the ultrasonic also stops(work with battery,Battery is not include)