There are several types of time and attendance software badge/card technologies available today. The following are the most common:
HOLLERITH - A plastic or paper card that has holes punched in it and is read optically. This is one of the earliest technologies and is mostly used as an encoded room key in hotels. They are not secure but are inexpensive to make.
BAR CODE - The use of bar codes is limited. There is no security, unless used with a bar guard (dark film affixed over the bar code can be read only with visible light reader). The bar code strip can be easily damaged but like Hollerith, are inexpensive to make.
MAGNETIC STRIPE - Used mostly by credit card companies, they have three tracks with two that are usable. Readers come either as track one or track two, or a combination reader reads all. More secure than barcode but easily damaged.
PROXIMITY - Hands-free operation is the primary selling point of this card. Although several different circuit designs are used, all proximity cards permit the transmission of a code simply by bringing the card near the reader (6-12”). Older cards are thick; up to 0.15” (the ABA standard is 0.030”) with newer cards thinner than normal bar code cards.
WIEGAND - Named after its inventor, this technology uses a series of small diameter wires that, when subjected to a changing magnetic field, induce a discrete voltage output in a sensing coil. Two rows of wires are embedded in a coded strip. When the wires move past the read head, a series of pulses is read and interpreted as binary code. This technology produces cards that are VERY hard to copy or alter, and they are moderately expensive to make. Card readers based on this technology are epoxy filled, making them immune to weather conditions, and neither the cards or the readers are affected by external magnetic fields.
D. David Waters - Clock Data Manager