What is wiegand?

MIFARE, RS232, RS485, Wiegand, 120 kHZ, UHF, EPC, clock and data, AES…

The access control world and vehicle identification is full of ideas, strategies, abbreviations and words that outside our industry, people frequently find hard to understand.

This article aims to clarify the word Weigand, as the term is applied to various features related to readers but also to access control cards. Often the word is misused and can lead to confusion.

An access control systems usually consist of:

  • RFID access control cards that, are read by
  • Access control RFID card readers nearby the door to protect, that are connected to
  • Access control panels (a physical controller), hardware that is able to open door locks and that is connected to
  • An access control management system (software) that manages building access credentials and authorizations.
  1. Proximity cards are programmed with a number. That number must be in a format that can be understood by the reader. It also needs to be known in the access control software or controller so that it can be processed. Usually, proximity cards have a facility code number and a card number. The facility code links the tag to a specific customer, installation, or country. The card number must be unique for the installation with that facility code and is used to identify a person (or a vehicule).
  2. The number is encoded in a specific way so that it can be sent wirelessly. This protocol of communication ensure that the card and the reader can understand each other.
  3. The encoded number is sent by radio waves at a specific frequency. Both the reader and the card should use the same frequency so they are able to communicate.
  4. The reader is physically connected through wires to the controller and to the software. The information sent from the reader to the controller is also encrypted. This encoding is what is called the communication protocol between the reader and in many cases, the communication protocol between the card and the reader is different from the communication protocol between the reader and the controller.

Why is there a Wiegand confusion?

The word Wiegand is often used without defining what it is referring to. The confusion originates from not knowing if it refers to:

  • Communication between a reader and a controller
    The encoding format of RFID cards

As we saw in point 4 of the scheme, many readers can read cards in Wiegand format, but then they can use other communication protocols and wiring between the reader and the controller.

In general, Wiegand usually refers to the communications between the reader and the controller.



The Wiegand effect refers to magnetic effect in specific wires, named after John R. Wiegand. It is used to encode or decode information.

Wiegand devices were originally developed by HID Corporation

This technology was created and patented by HID as a “secure” alternative to magnetic stripe cards. They are made of PVC and have the shape of cards or key rings inside which – during the manufacturing process – “magnets” are placed oriented in such a way that when the card get within reading range of a proximity readers, binary information is obtained that represents a number.

The main advantage of the Wiegand effect is that unlike magnetic cards, cards with a Wiegand effect do not demagnetize.


The Wiegand interface is a wiring standard commonly used to connect a card reader to the rest of an access control system.

The Wiegand interface uses three wires.

  1. DATA1
  2. DATA0
  3. GND

The communication protocol used in a Wiegand interface is known as the Wiegand Protocol.


The Wiegand protocol is a form of communication that was created, patented and introduced to the market by the company HID, it is essentially unidirectional and allows the transmission of data between a reader and a controller. The protocol establishes data lines, power and signaling.