The FGD0007 Passive Infrared Motion Sensor is ideal for use with all of our auto-dialers. The FGD0007 will monitor the movement of people in a specific area, which will then cause your auto-dialer to call you with an alarm message. This is a great security feature for your home or business. The range is a maximum of 40 feet directly ahead of, and approximately 20 feet to either side of, the detector at 40 feet distance (see installation instructions for diagram). Multiple sensors can be wired in series or parallel to a single input. Two "AA" batteries included.