The Trigg Industries Z-Pattern® OVERHEIGHT VEHICLE DETECTION SYSTEM (OVDS) employs both a pulsed visible Red and Infrared source/detector pair of eyes. As shown in Figure 1, Z-Pattern® Concept, both Remote and Master cabinets contain a detector and pulsed source. All Control, Fault Detection and Alarm functions are contained in the Master cabinet. The Dual Beam Detection Mode provides for direction selection/discernment. Due to the Z-Pattern® design, it is necessary to provide a two-conductor shielded cable between the Remote cabinet and the Master cabinet for the Remote detection signal input.

Fault detection circuits switch the OVDS to Single Beam Detection Mode if one beam should fail or be affected by the sun or other outside interference. The system will return to the Dual Beam Detection Mode after the temporarily impaired beam is back in normal operation for approximately 90 seconds. There is no direction discernment in the Single Beam Detection Mode but overheight detection is maintained.