Vehicle Detector. A single unit for all low voltages – 10 to 30 Volts AC or DC. The DSP-15 vehicle detector has been specifically designed to handle all parking, drive-through and access control applications. Working on virtually any size loop, the DSP-15 automatically tunes itself to the best operating frequency within the selected range. Environmental conditions are constantly compensated with the DSP-15’s HYPERTRACK software. The DSP-15’s inherent noise filtering algorithms allow it to work reliably in any electrical situation. Loop Size – Works on any in-ground inductive loop from 20 to 1000 mH.