Passive Proximity Cards
Commonly, security cards are read either by swiping through or inserting into a card reader. Proximity cards use Radio Frequency Identification (RFID) to approve or deny credentials with a reader that is within the card’s range. There are two types of proximity cards, the newer ones are 13.56 MHz contact-less cards, and the older ones are 125 Khz.
Proximity cards use resonant energy, which means they are able to send data without an energy device or battery. The card contains a capacitor and a coil, which are charged when it receives a radio signal from the card reader. The coil then charges the Integrated Circuit (IC), which stores the identification credentials. When the IC is charged, it uses the Wiegand Protocol to transmit the ID codes to the reader.
Active Proximity Cards
Active proximity cards have a more powerful identification transmitter that requires battery power. These Active transmit data to long range readers. They are commonly used for container tracking, toll roads, and vehicle tracking.
For more information about proximity cards and other access control topics, please check out Thomas L. Norman’s book Electronic Access Control.