This is from Whites. They get the credit. It is a good explanation.
How Metal Detectors Work
The V3i, V3, and VX3 are multi-frequency (MF) induction-balance (IB) very low frequencies (VLF) transmit-receive (TR) metal detectors. "VLF" Very Low Frequency refers to detectors operating below 30 kHz. This is the most popular technology at the present time. They represent the latest technology in metal detecting. There heart is a high-performance ARM-9 RISC microprocessor which simultaneously analyzes signals from 3 transmitted frequencies. Those frequencies
How Metal Detectors Work
The V3i, V3, and VX3 are multi-frequency (MF) induction-balance (IB) very low frequencies (VLF) transmit-receive (TR) metal detectors. "VLF" Very Low Frequency refers to detectors operating below 30 kHz. This is the most popular technology at the present time. They represent the latest technology in metal detecting. There heart is a high-performance ARM-9 RISC microprocessor which simultaneously analyzes signals from 3 transmitted frequencies. Those frequencies