Security Metal Detectors such as the Ranger product line, work very well—they are considered a solid technology and can accurately detect the presence of most types of metals, such as firearms and knives.
A security metal detector in security applications is used primarily to locate undesirable objects that are hidden on a person’s body. When a questionable item or material is detected by the device, the detector produces an alarm signal; this signal can be audible, visible (lights), or both..
Walk-through security metal detectors are common in airports, public buildings, and military installations. Their portals are bracketed with two large coils or loop-type antennae, one a source and the other a detector. Electromagnetic waves (in this case, low-frequency radio waves) are emitted by the source coil into the detection space. When the electromagnetic field of the transmitted wave impinges on a conducting object, it induces transient currents on the surface of the object; these currents, in turn, radiate electromagnetic waves. These secondary waves are sensed by the detector coil.
Some people fear the use of a metal detector on themselves because of the possible side effects of being subjected to the magnetic field. This fear is unfounded; metal detectors emit an extremely weak magnetic field, weak enough to be of no concern even to heart patients with pacemaker-type devices.
Another widely held belief about metal detectors is that they are a straightforward technology, where the equipment does all the work. This is not true at all. The average first-time consumer will undoubtedly expect a metal detector to be much smarter and more helpful than it can possibly be. A metal detector is only as good as the operator overseeing its use.
In many facilities, the misconception exists that someone known by the operator, such as a fellow employee or a security person, should be allowed to circumvent the system. It must be clearly established that in order to ensure the integrity of any routine metal detection program, everyone must be subjected to the program requirements, including students, parents, teachers, custodial and maintenance staff, security personnel (except for sworn police officers who are required to carry a weapon), school administrators, and visitors. To require less would be counterproductive and prejudicial. Signage can be of great help: a sign at the school entrance explaining the importance of the detectors in maintaining a safe and comfortable learning environment provides policy notification.