In security, there are three universally recognized factors for authenticating individuals:
- Something you know, typically a Personal Identification Number (PIN)
- Something you have, typically a security token (encoded credential).
- Something you are, such as a fingerprint, a retinal scan.
The more authentication used, the higher the security. But other considerations come into play when specifying how much security is being deployed. Based on the risk assessment, the cost to deploy and maintain the system may become a factor. Guards are expensive.
Inefficient authentication may result in throughput issues and lead to system abuses.High technology security can malfunction and lead to low throughput.
Credentials used in access control are:
- Magstripe: widely used but are considered too easy to clone
- Barrium Ferrite: obsolete and even easier to clone
- (Concealed) barcode: easiest to clone
- Weigand: Encoded, still used.
- Proximity: the most widely used type of credential
- Smart Cards: predicted to soon become the de facto standard in security credential technology.
Although the term Weigand is often used to describe a credential or a reader, this is sometimes referring to the format used to transmit the data that is read off the card by the reader back to the access controller.
The term Wiegand was originally used to refer to card reader technology which included the encoded credential, the reader and the interface (data format) between the reader and the access control electronics. 26 bit referred to the protocol of the data on the card.
Proximity credentials and readers currently hold the majority of the market share, and typically use the Wiegand interface and 26 bit encoding.
Weigand readers have a big disadvantage compared to proximity. Although the Weigand reader was sealed and extremely robust, performing a card read required physical contact between the reader and the credential to gain access, whereas the proximity does not. The need to manipulate the credential in the reader slowed down throughput. The proximity reader was far more convenient and reliable.
The other disadvantage was that the credentials had to be factory ordered, since they were encoded during the manufacturing process.
The evolution of the manufacturing engineering and the economies of scale (lowered cost as quantities increase) also contributed to Weigand’s loss of market, and proximity’s gain in popularity.
Unlike magstripe, where the ferrous material on the credential is magnetized with the data pattern, the Wiegand card is embedded with small wires in a specific pattern. When the card is passed through the magnetic field in the reader, measurable fluctuations in the wires embedded in the card are sensed by the reader sensor, and buffered into a Wiegand bit stream. The Wiegand Interface is a buffering circuit which generates data as “1” and “0” data pulses.
The Wiegand interface requires three conductors; DATA-1; DATA-0; and DATA RTN. Additional conductors are required if audible (beeper) and visual (LED) control on the reader is desired.
The DATA-1 and DATA-0 lines are held ‘high’ at 5 VDC, and go to ground in a pattern which represents the data on the credential. The timing of the pattern and other parameters of the data stream is generated by the Wiegand interface circuitry in the reader.
Some reader manufacturers indicate that 500-foot cable lengths between the reader and the access controller are allowable, and shielded multiconductor is specified. More conservative cable lengths are cited in access control product documentation, depending on the manufacturer. As a practical matter, if your controller is 500 feet from your door, you are going to have to deal with other performance issues besides bad card reads.
In difficult installation environments, reader performance can be enhanced by grounding the reader end of the shield. Also range extender and multiplexer modules are available for long cable runs or high noise environments which will provide good reader data transmission, and eliminate voltage drop problems.
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