PetSafe Bark Control - Outdoor Dog Bark DeterrentSilence incessant barking with the help of PetSafe's Bark Control an outdoor deterrent for dogs that looks like a birdhouse. Emitting a harmless ultrasonic sound when activated, this discreet unit can be hung on a tree or fence post to cover up to 1 4 acre of space. With three settings and a test option, it's an effective tool for training and keeping peace in the neighborhood. Weatherproof and powered by a 9 volt battery, it's a reliable solution for