The detector is based on a technology developed by the Idaho National Engineering Environmental Laboratory. It uses extremely sensitive instruments called fluxgate magnetometers to sense, measure, and define any aberrations or anomalies in the magnetic field in order to locate and characterize underground structures. The technology has been adapted for use in detecting concealed weapons. The portal produces a top-to-bottom image of the person passing through it. The image is sent to a control room where a security guard views it on a split screen. Half of the screen portrays the person inside the portal while the other half divides the body image into grids to show where a concealed object is located. Access to a secure area is denied by use of a remote-controlled entry door until the officer is satisfied that the individual does not possess any weapon. The detector's use at the Bannock County Courthouse (Idaho) has been effective in detecting a variety of weapons. On any day, the portal quickly scans 500-600 people. One advantage of the system is that it takes only one security officer to monitor the three courthouse entrances. Three computer screens are inside the control room and are constantly viewed by security personnel, who can communicate with those passing through the portals via an intercom.