Electronic Article Surveillance Systems (EAS) belong to the RFID systems (Radio Frequency IDentification). For reasons of clarity, the EAS systems are seperated in an own category. EAS systems are often called a one-bit-RFID system as long as only the appearance of a tag is detected. More-bit-RFID systems transmit, for example, an identification number of the tag, but can be used as an EAS system, too.
The basic principle of an EAS is based on a tag that is attached to the good that needs to be protected against shoplifting an pilferage. This tag can be incorporated into the good by the manufacturer like, for example, in the heel of a shoe. In case of a purchase of the good this tag is either removed or deactivated at the checkout counter. Transmitting and receiving antennas (detectors) are arranged in the exit area (after the checkout counter) which emit a magnetic or electromagnetic field that needs to be passed by the customer. When an active tag is carried through this field (e.g. a not paid good) the tag interferes with the field and is detected by the antennas. In general this results in an alarm.
Depending on the technology the tags can be distinguished in active and passive tags, depending on the energy supply of the tag. Active tags use a battery, thus are bigger, more expensive and emit an own field, which can be detected by the receiving antennas in the exit area. The passive tags are either supplied by the transmitting antennas in the exit area or manipulate the field of the transmitting antennas. In the absence of a battery these passive tags are more cost efficient and smaller which makes them suitable for shops with a large set of goods, but the transmission range is smaller than of active tags.
The used frequency ranges of the EAS systems are dependent on the used technology. These technologies have established: radio frequency systems use frequencies between 1.8 and 8.7 MHz; microwave systems in the ISM-band around 2.45 GHz and 5.8 GHz; electromagnetic systems between 10 Hz and 20 kHz; acousto-magnetic systems at typically 58 kHz.
The most often used systems are the radio-frequency systems and the acousto-magnetic systems.