For years, people have been hammering on the cliff to get valuable material from the Earth's surface. It could be coal, ore, diamonds and other minerals, but at this time the metal detectors were crude and primitive. He just feels the ground and hears the sound that will determine if there's anything below it. Until the 1930s, engineers were able to develop a system based on radio frequency. It was better than using the hammer in the past, but the device was very heavy and carried the back of a heavy battery.
This machine has improved further during the Second World War. The soldiers use it to clean up the area of landmines so that the troops can advance forward. The metal detector proved to be useful again when changes occurred in the 1970s, causing airports and other vital facilities to be able to cope with such a threat.
Today, the security metal detector comes in all shapes and sizes. Security personnel may use a stationary machine where the person has to pass over knives, bombs and hidden weapons. In places where this is not applicable, the manual version can be used.
Users of security metal detectors can increase the sensitivity of the machine. This means that the alarm sounds even if the person has a button, a cell phone or a coin in his pocket.
You just have to show one of those at the gate before going on.
But the metal detector is not only used for safety. Hobbists and archaeologists also use this or find buried treasures or artefacts. Various models are available and high-tech versions can determine the size, weight, and description of the object even before it is explored.
The difference between the terms used by security and hobbies is that persons assigned to certain posts may not use headphones. If they find something, people there call on the person to empty the pockets and walk through the machine again so that there is no problem.
If the alarm still sounds, there may still be something on the person or a problem with the device.
Metal detectors are simply looking for minerals for military and civil use, and it will continue until a better machine comes out of the old system.