VLF stands for Extremely Lower Frequency and is similar technological know-how used in detectors designed for cash, jewellery, and relics. VLF detectors broadcast at frequencies calculated in kilohertz starting from three kHz to 70 kHz. Listed below are 5 explanations why you could possibly pick a VLF over a PI http://nec.phorum.pl/viewtopic.php?p=753869#753869