VLF (Very Low Frequency) is a conventional single frequency sine wave transmission technology. This is the traditional type of technology used in most basic metal detectors. Single frequency sine wave detectors create an electro-magnetic field, which is transmitted into the ground in a continuous wave. While the basic way that the signal is sent out and received back has not changed, the receive signal processing has improved enormously. This has proven to be a reliable and easy to use technology for finding gold.