Proximity card

A proximity card or prox card is a "contactless" smart card which can be read without inserting it into a reader device, as required by earlier magnetic stripe cards such as credit cards and "contact" type smart cards. The proximity cards are part of the contactless card technologies. Held near an electronic reader for a moment they enable the identification of an encoded number. The reader usually produces a beep or other sound to indicate the card has been read. Proximity cards typically have a read range up to 50 cm (< 15 inches) which is the main difference with contactless smartcard with 2 to 10 cm (1 to 3 inches) . The card can often be left in a wallet or purse, and read by simply holding the wallet or purse near the reader. The term "proximity card" refers to the older 125 kHz devices as distinct to the newer 13.56 MHz contactless smartcards.

Proximity cards can't hold more data than a magnetic stripe card. Only contactless smartcards can hold other type of data like electronic funds balance for contactless payment systems, history data for Time & Attendance or biometric templates. When used without encoding data, only with the Card Serial number, contactless smartcard have similar functionalities to Proximity cards.

Passive 125 kHz cards, the more widely used type which were described above, are powered by radio frequency signals from the reader device and so have a limited range and must be held close to the reader unit. They are used as keycards for access control doors in office buildings. Contactless smartcards are used for all other applications: library cards, contactless payment systems, and public transit fare cards.

Active 125 kHz Prox cards, sometimes called vicinity cards, are powered by an internal lithium battery. They can have a greater range, up to 2 meters (6 ft). Other contactless technologies like UHF (Ultra High Frequency) can reach up to 150 meters (500 ft) and are often used for applications where the card is read inside a vehicle, such as security gates which open when a vehicle with the access card inside approaches, or automated toll collection. The battery eventually runs down, however, and the card must be replaced after 2 to 7 years.

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Wikipedia