Now you can have a vicious dog greet anyone who approaches your home when you are not there, scaring off would-be intruders without the cost of dog food, vet bills, etc. A recording of a German Shepard in attack mode begins to play when motion is detected. This alarm is very effective for home, office, factory or any place that needs the constant security of a guard dog. Please note that it will sense motion through almost any type of wall (wood, cement, brick, stucco, glass, etc.) but will not work through metal walls, walls with metal studs, tinted glass, ultra thick barriers, or electronic devices. The Streetwise Electronic Watch Dog emits microwave signals so it can "see" through walls and detect someone approaching from up to 21 feet away. If the intruder continues to approach the house, the barking will get louder and more frequent. Unit can also be set to chime or alarm instead of bark. It is powered by a 12 volt wall adapter (included), but you can also use 8 AA batteries (not included) for backup or for areas without a plug. Includes a wireless remote control to allow you to arm/ disarm the unit from a distance as well as sound a panic alarm in case of emergency. It has an adjustable volume and detection range (up to 85 decibels and 21 feet depending on the type and thickness of the barrier) and measures 7 x 6 x 4 inches. Covered under a year warranty.