Card Readers

Access control card readers are used for reading data embedded in cards to allows access through access control points, typically a locked door. An access control reader can be a magnetic stripe reader, a bar code reader, a proximity reader, a smart card reader, or a biometric reader.

Barcode Readers

A barcode is a series of alternating dark and light stripes that are read by an optical scanner. The organization and width of the lines is determined by the bar code protocol selected. Barcode Protocol 39 is the most popular in the security industry. Barcode is cheaper and easier to generate and can be easily applied to cards or other items. However the same affordability and simplicity makes the technology susceptible to fraud, because fake barcodes can also be created cheaply and easily, for example by photocopying real ones. Hence it is not commonly used for access control.

Biometric Readers

Biometric Readers may utilise fingerprints, hand geometry, iris or facial feature of a user to identify the user.  An initial scan is stored in a template and used to compare with subsequent scans to determine the identity of the user.  This method is generally preferred by most end users because it eliminates the need to carry ID cards or use PINs.

On the other hand this method is slower, because the reader may have to perform thousands of comparison operations until it finds the match, particularly for large installation with many users. Currently most 1-to-many readers are capable of performing 2000-3000 matching operations in one second. In the 1-to-1 mode a user must first identify himself/herself to the reader by either presenting an ID card or entering a PIN. The reader then looks up the template of the user in the database and compares it with the live scan. The 1-to-1 method is considered more secure and is generally faster as the reader needs to perform only one comparison. Most 1-to-1 biometric readers are "dual-technology" readers: they either have a built-in proximity, smart card or a keypad reader.

Magnetic Stripe Readers

Magnetic stripe technology encodes data on the stripe of magnetic oxide tape that is laminated on a card. The data on each of the tracks follows a specific encoding standard, but it is possible to encode any format on any track. A mag-stripe card is cheap compared to other card technologies and is easy to program. The magnetic stripe holds more data than a bar code can in the same space. While a mag-stripe is more difficult to generate than a bar code, the technology for reading and encoding data on a mag-stripe is widespread and easy to acquire. Magnetic stripe technology is also susceptible to misreads, card wear, and data corruption. 

Wiegand Card Readers

Wiegand card technology is a patented technology using embedded ferromagnetic wires strategically positioned to create a unique pattern that generates the identification number. Like magnetic stripe or bar code, this card must be swiped through a reader to be read. Unlike those other technologies the identification media is embedded in the card and not susceptible to wear. This technology once gained popularity because of the difficulty in duplicating the technology creating a high perception of security. This technology is being replaced by proximity cards because of the limited source of supply, the relatively better tamper resistance of proximity readers, and the convenience of the touch-less functionality in proximity readers.

Proximity Card Readers

A Proximity card reader radiates a 1" to 20" electrical field around itself. Cards use a simple LC circuit. When a card is presented to the reader, the reader's electrical field excites a coil in the card. The coil charges a capacitor and in turn powers an integrated circuit. The integrated circuit outputs the card number to the coil which transmits it to the reader.

A common proximity format is 26 bit Wiegand. This format uses a facility code, sometimes also called a site code. The facility code is a unique number common to all of the cards in a particular set. The idea is that an organization will have their own facility code and a set of numbered cards incrementing from 1.  To prevent duplication of cards, manufactures have created formats beyond 26 bits.