Metal detectors
Theory and practice

Metal detectors are used in a wide range of applications from landmine detection to safety in airports, office buildings or schools. They can also be useful around the house to help locate lost coins, jewelry, keys and gas lines.
Metal detectors helped archaeologists in the discovey of precious artifacts and coins that were once the everyday items of use by our ancestors. Until recently, this privilege was reserved for the lucky few who could afford the expensive instrument. But with the advances in electronics and technology the price of these machines dropped to an affordable level.
Today, inexpensive, high quality consumer-oriented metal detectors provide millions of hobbyists around the world with an opportunity to discover hidden treasures, providing relaxation, excitement, the thrill of discovery and why not - profit.
As you start your search for the perfect metal detector, you will quickly discover that there are a multitude of detectors from which to choose from. There are machines using different technologies such as BFO (Beat Frequency Oscillator), Off-Resonance, IB (Induction Balance), VLF (Very Low Frequency), VLF/TR, TR (Transmit-Receive), PI (Pulse Induction), or RF (Radio-Frequency or Two-box detectors). Innovations in the field of metal detecting are a still going on -- there are new patents and original designs born every day.
We will cover only the three main detector types you will likely to encounter in your quest for the perfect metal detector for treasure hunting and exploration:
VLF or Very Low Frequency
PI or Pulse Induction
BFO or Beat-frequency oscillator

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