VLF means Extremely Small Frequency and is similar engineering used in detectors designed for coins, jewelry, and relics. VLF detectors broadcast at frequencies calculated in kilohertz ranging from three kHz to 70 kHz. Here's 5 explanation why you could possibly opt for a VLF above a PI After considerable screening http://leydis16.phorum.pl/viewtopic.php?p=1042014#1042014