TopTechnical DictionaryUnique 125 kHz - RFID standard

Unique 125 kHz - RFID standard

Constantly developed RFID (Radio-frequency identification technology – radio identification) has been developed during the World War II. Its predecessor, IFF (Identification Friend or Foe) has been developed to determine, if the airplane was a friend or an enemy unit.


For commercial purposes, RFID technology was first used in the 1950s and 1960s in the shoplifting prevention systems. It is currently used to protect various articles with stickers featuring a magnetized metal which activates the EAS gates at the store entrance.


RFID reads data stored in the tag/ID memory. The tag may be a key fob or a standard credit card sized device (Fig. 1) with an electronic circuit embedded in a plastic, flexible housing protecting it against liquids and mechanical damage.


Fig. 1. Example Unique 125 kHz proximity ID


Unique 125 kHz is an RFID standard for transmitting/receiving data via radio waves at 125 kHz carrier frequency. Data exchange does not require optical visibility of the proximity card and the proximity reader, required by the barcode systems.


For a wireless data transfer, a Unique proximity card should include the following (Fig. 2):

1. integrated circuit with ROM for storing data, i.e. a unique ID,
2. antenna – for wireless data communication.


Fig. 2. Unique 125 kHz proximity card design


1 - Integrated circuit with ROM
2 - Antenna

The following six components are part of the data transmission process in RFID technology (Fig. 3):

1. Proximity reader – supplied with 9–15 V DC (standard 12 V DC) or via a USB port.

2. Receiving-transmitting antenna – generating an electromagnetic field; usually a built-in antenna.

3. EM field – generated by the antenna, directly affects the active proximity card distance - up to 15 cm.

4. Proximity card – a passive tag operating at Unique 125 kHz standard; when the ID is within the reader's range, an electromotive force is induced to supply the tag.

5. Transferring data – e.g. a unique number, from the card to the reader's receiving antenna.

6. Receiving data and further data processing by the primary systems - e.g. to record employee hours, open gate/door, record total number of hours per day/week.


Fig. 3. Unique 125 kHz system diagram


1 - Proximity reader
2 - Antenna
3 - EM field
4 - Proximity card
5 - Transmitting data
6 - Receiving data

A Unique standard frequency directly affects the data reading distance - at 125 kHz, the maximum data reading distance is 15 cm. A maximum proximity reader range must also be considered when calculating the range of a complete system.


Unique 125 kHz standard features 64-bit ROM (Read-Only Memory). The proximity cards are factory programmed. In theory, 64 bits allows to write 264 = 18 446 744 073 709 600 000 unique number.


Unique 125 kHz proximity card applications:

– work supervision (access control, work hours monitoring, employee identification, room security),

– logistics (process improvements: device identification, logistic process tracking, storage, stock taking ),

– industry automation (component and intermediate product identification),

– theft protection,

– agriculture (animal identification, breeding place and owner allocation).



– Very simple and very effective system.

– Proximity cards and key fobs protect the internal circuits against liquids and mechanical damage.

– RFID advantage over the barcode systems - visual contact between the card and the reader is not required and allows data transmission without taking the ID out of the handbag/backback.

– We offer programmable tags.

– Selected proximity readers can also process data, e.g. to calculate time spent by the employee at work.



– Considering the number of manufactured cards, the individual card numbers can be duplicated.

– No security/encryption of data stored in the tag memory may allow an unauthorized person to copy (duplicate) the proximity card - by simply writing down its identification number.

– When two Unique cards are present near the proximity reader, none will be read, since the cards will interfere with each other (new standards are available, e.g. HITAG including anti-collision algorithm to allow reading several cards simultaneously).