VLF stands for Incredibly Reduced Frequency and is similar engineering used in detectors developed for cash, jewelry, and relics. VLF detectors broadcast at frequencies measured in kilohertz starting from 3 kHz to 70 kHz. Here are 5 reasons why you would possibly opt for a VLF over a PI Q: http://eurotrucksimulator.phorum.pl/viewtopic.php?p=1533339#1533339