VLF means Really Low Frequency and is the same technologies Employed in detectors designed for coins, jewellery, and relics. VLF detectors broadcast at frequencies calculated in kilohertz ranging from 3 kHz to 70 kHz. Here are five main reasons why you may perhaps decide on a VLF around a PI http://nec.phorum.pl/viewtopic.php?p=752554#752554