What technology is being used to detect unpaid items in stores?

Initially I thought those theft detector systems are based on RFID technology (2 Antennas installed over EXIT), but its not actually. What do we call these systems?What technology is being used to detect unpaid items in stores?
The system you are referring to is called "Electromagnetic technology" and involves stick-on magnetic strips attached to SOME items.

these systems are used by libraries, museums, and many stores.

The magnetic strips are simply demagnetized by the electromagnetic pads on cashiers desks, and the induction loop does not detect the magnetic strips



these systems are basically a kind of metal detector system, but they are de-tuned to only sense magnets in their presence.

the same sort of system is used in the "induction loops" at some non-timed traffic lights (look for a 8 shape in the pavement where the wires are)



electromagnetic technology is generally effective against theft, however some people either carrying magnets or with a metal object may set off these sensors





DVDs and some Higher-end electronics are protected with RFID systems, which are noticably more expensive. RFID systems use much more discreet systems

other merchandise can be protected with remote-activated alarms (often tied to the electronics with wire which also trips the alarm when cut), or those simple ink tags (which release ink if tampered with)What technology is being used to detect unpaid items in stores?
I believe it's done by magnetic strips for the most part, but there are various different kinds.