Card reader

Lore & Background

The earliest example of a punched card reader, the Jacquard machine, physically pressed punched cards against rows of mechanical control rods to convert the data on the cards into physical positions of the loom's hooks. A hole in the card would allow the rod to pass through and remain unmoved; if there was no hole the rod would be pushed, moving its hook out of position. Beginning with the Tabulating machine in 1890, data was read from punched cards by detecting whether a hole in the card allowed an electrical circuit to connect or an unpunched section of card interrupted that circuit.

Magnetic stripe technology, usually called mag-stripe, is so named because of the stripe of magnetic oxide tape that is laminated on a card. There are three tracks of data on the magnetic stripe. A mag-stripe card is cheap compared to other card technologies and is easy to program. The magnetic stripe holds more data than a barcode can in the same space. Magnetic stripe technology is also susceptible to misreads, card wear, and data corruption. These cards are also susceptible to some forms of skimming where external devices are placed over the reader to intercept the data read.

Smart card readers use an electrical current to read data from embedded circuitry or magnetic features in a card. A contact smart card must physically touch contacts on a reader to connect a circuit between them. A contactless smart card uses radio waves or a magnetic field to transmit information to a reader remotely. Contactless smart cards do not require physical contact with the reader and can function through materials like wallets or purses, typically within a range of 20 inches or less. Proximity card readers radiate a 1 to 20 inch electrical field around themselves. 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, which charges a capacitor and powers an integrated circuit that outputs the card number to the reader.

Reader's Guide

Card readers have been significant across multiple domains including identification, access control, banking, data storage, and data processing. The variety of mechanisms—from mechanical punched card readers to electrical, magnetic, smart, and contactless technologies—reflects the evolution of data storage and retrieval. Magnetic stripe technology became widespread due to its low cost and ease of programming, though it remains vulnerable to wear, misreads, and skimming attacks. Smart card readers introduced enhanced security through embedded circuitry and contactless communication, enabling applications such as electronic payments and biometric verification without physical contact. Proximity card readers, often still called 'Wiegand output readers', retain compatibility with older systems while offering touchless convenience. The legacy of card readers includes their role in early computing via punched cards, their continued use in modern access control and banking, and their adaptation to new security challenges such as supply chain attacks targeting smartcard readers. Memory card readers have become common peripherals for accessing data on formats like CompactFlash, Secure Digital, and MultiMediaCard, often using USB interfaces.

Did You Know?

• The earliest punched card reader was the Jacquard machine, which used mechanical control rods pressed against cards.
• Magnetic stripe cards have three tracks of data and are susceptible to skimming via external devices placed over the reader.
• Contactless smart card readers operate at 13.56 MHz and can communicate with multiple cards simultaneously using anti-collision protocols.
• The 26-bit Wiegand format uses a facility code and card number with parity bits for error checking.