Anti-theft systems installed at the exit of the shops are of two types. The first one consists of a magnetic label that sticks in articles, and its operation is based on the detection of the disturbance of a magnetic field. The bumper includes a tiny coil that produces a local magnetic field when entering domains magnetic field detector, the two metal arches located outside the property.
The magnetic area is generated by the electric current flowing through the coil. If the tag has not been deactivated by a dependent, causes an alteration of the magnetic field that triggers the alarm. The second system consists of a clamp or a plastic box that hooks or enclosing the article and hidden carries a miniature radio transmitter consisting of one coil of copper wires and various electronic components.
When the protective passes through the magnetic detector located off trade field, the coil produces an electric current that feeds electronic components, and these generate a radio signal which is picked up by the receiver to activate the alarm.