Low Frequency: what is 125-134 kHz passive RFID technology?

LF (Low Frequency) operates in the 125–134 kHz range. This is the lower end of the radio frequency spectrum. LF was the first used for automatic identification: its market presence is still very significant today.

Low Frequency 125-134 kHz is widely used for its characteristics:

• Well-defined magnetic field. 
  The magnetic field of the LF band has no dispersion, modulation or refraction.  
• Works well in the presence of metals
  Low Frequency RFID tags can be read near or above metals, since the signal emitted by the reader cannot pass through them. 
• Good capacity to pass through materials
  The Low Frequency signal can pass through any type of material, except, of course, metal.
• Little affected by liquids
  One limitation of radio-frequency technology is its inability to function in the presence of liquids; however, low frequencies (125–134 kHz) are little affected by them. 
• Proximity reading
  The LF band is suitable for proximity readings at a distance of 10–15 cm. 
• Low tag reading/writing speed, making accurate readings possible
  In the low-frequency band, tag reading and writing are carried out slowly, which is why low frequencies can be used when precise readings are required. 

RFID cards are popular for access control at hotels and campsites, gyms, companies, schools, universities, and sports federations. They contain a 125-kHz chip, the contactless card can be detected at a distance of a few centimetres and the system guarantees high-performance reading. As an alternative to cards, RFID key fobs and wristbands also contain a 125-kHz chip. They have the same reading and operating features as RFID badges.

Low-frequency RFID cards and key fobs are also popular for opening car park barriers and electric gates. Reading occurs by bringing the card close to the reader to open the gate or barrier. 

Low-frequency 134 kHz is the standard technology used to identify domestic animals (compulsory for dogs) and farm animals (cows, pigs, horses, etc.). The choice of low frequency is due to the fact that it is not affected by liquids. In fact, animals’ bodies, like humans’, consist of a high percentage of water. Vets administer 134-kHz tags to the animals with food, by injection or inserting them subcutaneously.

RFID cards, key fobs and wristbands with 125-kHz chips are used as electronic wallets to store credit that can be spent at self-service machines that automatically dispense products and services, including vending machines, laundromats, self-service car washes and water refilling stations. And again, LF RFID badges and key fobs are useful for charging electric cars at charging posts. Payment is made and electricity is supplied by bringing the card or key fob close to the charging symbol on the post, which is equipped with an RFID reader.

Controlled access bins are widely used in municipalities that apply door-to-door pay-as-you-throw waste collection, which calculates the variable part of the fee based on the amount of unsorted waste delivered by the user. The bin is opened by means of an RFID card containing a low-frequency chip, which allows user identification. 

Since metal and liquids have little influence on the low-frequency band, RFID hard tags are used in the industrial sector to identify objects containing metal or liquid. Other industrial applications include automated production processes, the detection of interference from monitors and industrial installations.