Xtreme Research Skyscan Lightning/Storm Detector Powered by two 9V batteries (not included): automatic shut-off after five hours of continuous operation Rugged ABS plastic Detect the presence of lightning/thunderstorm activity occurring within 40 miles of your location Severe thunderstorm alarm and emits a distinctive 15 second continuous audible tone different from the detection of normal lightning activity Accurate to within 1 to 2 miles 97 percent of the time Powered by two 9-volt batteries (not included) for 40 - 70 hours of operation