Operating Radar Detectors in commercial vehicles is illegal in all states. Some states and provinces prohibit Radar Detectors also in passenger cars. Hill Country Research offers two models of Radar Detector Detectors to help enforce the law. The single beam MD-3/S detects the presence of a radar detector in front of the patrol car. The MD-3/D has two antennas and receivers, and provides information about the direction of the offending Radar Detector. This information is presented by two semicircle red LED bars and two sets of audio signals.