Enjoy a Quieter Environment With Intellipet™ Bark Solvers Put an end to nuisance dog barking with our Intellipet Bark Solver! Bark Solver units can be wall- or shelf-mounted inside or out. An ultrasonic correction tone sounds each time dogs bark. Sensitivity adjustment controls how loud the bark must be to trigger the tone. Frequency adjustment allows for selection of either ultrasonic sound (inaudible to most humans) or a sound audible to both dogs and humans. Bark Solver X40 is designed for outdoor use only and features battery operation for more flexibility in placement. Uses four "D" batteries (not included). Stronger transmission signal is ideal for partially deaf dogs or dogs up to 40 feet away. Bark selector allows the unit to be activated after 1-5 barks. Includes a cone to focus correction towards barking, and a wall-mount bracket. Measures 4 1/4" L x 4 1/2"W x 8 1/4"H. Bark Solver X40 includes a one-year warranty. Bark Solver X25 designed for indoor use is also available and sold separately