Proximity cards came about as a more convenient and more secure replacement to magnetic swipe cards for electronic access control. HID Proximity cards provided a more secure access solution and a more convenient user experience.
Contactless Proximity Technology
How do these cards prox work? Basically, the card is a low-power radio transmitter which sends a code to the reader. The reader determines if the code is valid and if the holder has the appropriate access rights. If so, it grants access by unlocking a door or taking some other action.
This kind of card is known as an RFID (radio frequency identification) card. RFID is a very widely used technology, with uses as varied as tagging merchandise and identifying pets. Modern technology has made RFID circuits low in cost and small enough to fit in almost anything.
The card contains a chip with a programmed code and a printed-circuit antenna. Most contactless cards don’t have their own batteries. The reader emits an electromagnetic field, called the excite field. It provides the small amount of power the card needs.
Proximity cards are also called contactless cards. Some people make the distinction that a contactless card interacts with the reader rather than just sending a code, but the terminology isn’t consistent. “Contactless smart cards” are definitely distinct from proximity cards.
With most models, the card has to be within a couple of inches of the reader to receive enough power and transmit a signal. The short read range makes it very hard for anyone to intercept the signal.
When a card receives power from the reader, it transmits its code. It’s in an encrypted form containing the holder’s ID and other data. Only the reader has the decryption code, so it’s very hard to forge a card.