Definition: Also see: Top 5 Travel Safety Sources on the Web
The use of metal detectors to identify weapons such as knives and guns, as well as mines, has made them a key anti-terrorism and airline security technology.
Although metal detection technology continues to be refined, all metal detectors rely on the magnetic induction principle, in which a magnetic object (such as metal, which is always magnetic), can magnetize a second object simply by their proximity.
This is why metal detectors at airports are held close to passengers' bodies: the detector is "reading" the magnetic field produced by watch chains, belt buckles and?potentially?weapons.
In 1973, American law began requiring passengers boarding American airline flight to pass through metal detectors. Originally, metal detectors were tunnels through which passengers walked for several feet.
Despite initial questions about possible violations of the Constitution's 4th Amendment barring illegal search and seizure, U.S. courts determined that if applied universally, metal detector searches are legal.
Metal detectors are also used to locate weapons, including land mines.
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