The Wiegand interface is a de facto

De facto

De facto is a Latin expression that means "concerning fact." In law, it often means "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established." It is commonly used in contrast to de jure when referring to matters of law, governance, or...

 wiring standard which arose from the popularity of Wiegand effect

Wiegand effect

The Wiegand effect is a nonlinear magnetic effect, named after its discoverer John R. Wiegand, produced in specially annealed and hardened wire called Wiegand wire....

 card readers in the 1980s. It is commonly used to connect a card swipe mechanism to the rest of an electronic entry system. The sensor in such a system is often a Wiegand wire based on the Wiegand effect discovered by John R. Wiegand

John R. Wiegand

John R. Wiegand discovered the Wiegand effect, a physical phenomenon in which a specially constructed Wiegand wire can detect small magnetic fields. The Wiegand wire is commonly used as a sensor to read security access cards. There is also a Wiegand Protocol commonly used to transmit the data...

. A Wiegand-compatible reader is normally connected to a Wiegand-compatible security panel.

Physical layer

The Wiegand interface uses three wires, one of which is a common ground and two of which are data transmission wires usually called DATA0 and DATA1 but sometimes also labeled Data Low and Data High. When no data is being sent both DATA0 and DATA1 are at the high voltage. When a 0 is sent the Data Low wire (also called DATA0) is at a low voltage while the Data High wire stays at a high voltage. When a 1 is sent Data High is at the low voltage while Data Low stays at the high voltage.

The high voltage level is usually +5VDC to accommodate for long cable runs (most reader manufacturers publish a maximum of 500 feet) from the door readers to the associated access control panel typically located in a secure closet.

Protocol

The communications protocol used on a Wiegand interface is known as the Wiegand protocol. The original Wiegand format had one parity bit, 8 bits of facility code, 16 bits of ID code, and a trailing parity bit for a total of 26 bits. The first parity bit is calculated from the first 12 bits of the code and the trailing parity bit from the last 12 bits. However many inconsistent implementations and extensions to the basic format exist.

An advantage of the Wiegand signaling format is that it allows very long cable runs, far longer than other interface standards of its day allowed.

See also

• Access badge
  Access badge
  An access badge is a credential used to gain entry to an area having automated access control entry points. Entry points may be doors, turnstiles, parking gates or other barriers....
  
  
• Access control
  Access control
  Access control refers to exerting control over who can interact with a resource. Often but not always, this involves an authority, who does the controlling. The resource can be a given building, group of buildings, or computer-based information system...
  
  
• Keycard
• Common Access Card
  Common Access Card
  The Common Access Card is a United States Department of Defense smart card issued as standard identification for active-duty military personnel, reserve personnel, civilian employees, other non-DoD government employees, state employees of the National Guard, and eligible contractor personnel.The...
  
  
• Credential
  Credential
  A credential is an attestation of qualification, competence, or authority issued to an individual by a third party with a relevant or de facto authority or assumed competence to do so....
  
  
• Identity document
  Identity document
  An identity document is any document which may be used to verify aspects of a person's personal identity. If issued in the form of a small, mostly standard-sized card, it is usually called an identity card...
  
  
• Magnetic stripe card
  Magnetic stripe card
  A magnetic stripe card is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card...
  
  
• Photo identification
  Photo identification
  Photo identification is generally used to define any form of identity document that includes a photograph of the holder.Some countries use a government issued card as a proof of age or citizenship.Types of photo ID cards include:*Passports...
  
  
• Security
  Security
  Security is the degree of protection against danger, damage, loss, and crime. Security as a form of protection are structures and processes that provide or improve security as a condition. The Institute for Security and Open Methodologies in the OSSTMM 3 defines security as "a form of protection...
  
   (physical
  Physical security
  Physical security describes measures that are designed to deny access to unauthorized personnel from physically accessing a building, facility, resource, or stored information; and guidance on how to design structures to resist potentially hostile acts...
  
  , engineering
  Security engineering
  Security engineering is a specialized field of engineering that focuses on the security aspects in the design of systems that need to be able to deal robustly with possible sources of disruption, ranging from natural disasters to malicious acts...
  
  )
• Proximity card
  Proximity card
  Proximity card is a generic name for contactless integrated circuit devices used for security access or payment systems. The standard can refer to the older 125 kHz devices or the newer 13.56 MHz contactless RFID cards, most commonly known as contactless smartcards.Modern proximity cards...
  
  
• Security
  Security
  Security is the degree of protection against danger, damage, loss, and crime. Security as a form of protection are structures and processes that provide or improve security as a condition. The Institute for Security and Open Methodologies in the OSSTMM 3 defines security as "a form of protection...
  
  
• Smart Card
  Smart card
  A smart card, chip card, or integrated circuit card , is any pocket-sized card with embedded integrated circuits. A smart card or microprocessor cards contain volatile memory and microprocessor components. The card is made of plastic, generally polyvinyl chloride, but sometimes acrylonitrile...
  
  

External links

• SIA Standard, AC-01-1996.10 - Access Control - Wiegand
• A Bidirectional Wiegand protocol Interface Converter
• Another description of the Wiegand protocol (timing diagram on page 5)
• Wiegand Technology: An Overview from vendor Mercury Security
• LayerOne 2007 - Zac Franken - Wiegand Hacked (Video on Youtube)
• US Patent, System and Method of Extending Communications With the Wiegand Protocol
• US Patent, Device Authentication Using a Unidirectional Protocol
• US Patent, Secure Wiegand Communications