RFID / NFC

RFID is a technology for reading information without physical contact. Data can be read from tags, which come in many different formats – the most common are cards (the size of regular payment cards) and key‑fobs. Other options include rings, stickers/labels, and more.

There are three main types of RFID: low frequency (LF, 125 kHz) and high frequency (HF, 13.56 MHz). And ultra high frequency (UHF, 868 MHz). In all technologies, the IC (which stores the data) can be powered wirelessly by an electromagnetic field. When the tag (and its circuit) is held within the field, the circuit receives power and automatically sends the data it contains. Tags with active power supplies are sometimes used, especially in 868 MHz RFID.

The technologies differ in several ways:

125 kHz is the simplest type of RFID. While limited, it is somewhat more reliable, with better range (up to 10 cm or more, depending on the reader).

RFID chips in the 125 kHz range are always read‑only. This means that – for better or worse – data can’t be written to them. Instead, each tag has a unique 64‑ or 128‑bit serial number. These IDs can be used as a form of unique barcodes. Some cards/fobs also have unique numbers printed on them.

125 kHz RFID is mainly used in systems without high security requirements: for opening doors, lifts/elevators, gates; in library cards; for clocking in/out at work, animal identification, etc. Common chips for 125 kHz RFID include EM4100 and EM4200 (which is backward‑compatible with the 4100).

13.56 MHz is a more advanced form of RFID. The chips in this system are not just preprogrammed memories, but rather, basic microcontrollers. 13.56 MHz chips can handle more advanced protocols, and the system supports encryption and authentication. Because they use microcontrollers, many tags are writeable, allowing you to store your own information on them. Some, however, are write‑protected from the factory. The system has a slightly shorter range than 125 kHz and is more easily blocked by objects.

13.56 MHz systems are used in payment cards, public transport cards, and more security‑sensitive access systems.

868 MHz (UHF RFID) differs from the other two technologies in that active tags are more commonly used. This is due to the system’s long range – up to 10–30 meters depending on the antenna and environment. At such distances, there isn’t enough energy to power the tag. Many UHF tags can still be run as “passive” devices at shorter distances.

UHF RFID is often used for larger objects that cannot be brought to a reader. For example, it can be used to identify vehicles for tolls and parking systems, keep track of locomotives on railways, for theft prevention, and for tracking objects that are moved around, such as hospital beds and other wheeled equipment.