VLF stands for Really Very low Frequency and is identical technological know-how Utilized in detectors built for cash, jewellery, and relics. VLF detectors broadcast at frequencies measured in kilohertz starting from three kHz to 70 kHz. Here's 5 explanations why you could possibly go with a VLF around a PI http://classichonda.phorum.pl/viewtopic.php?p=176963#176963