What is an HID Proximity Card and How Does It Work

Proximity cards are a type of smart card that make it easy to control access to and within a facility. They are physical devices containing a small antenna and programmed with credentials and are used in security systems for electronic authentication. Proximity cards are also known as prox cards and key cards. 

HID-brand prox cards are well-regarded within the industry, come in four different types suitable for a wide range of industries, and are widely used as part of a secure access control suite.

HID Prox Card

What is a HID Prox Card?

An HID Prox card contains these components:

  • A physical casing
  • An antenna coil
  • An embedded integrated circuit

The integrated circuit is what makes prox cards so useful: this circuit can store data and also communicate with reader terminals, which is most often some kind of electronic door lock.

Prox cards allow access control not just into a facility but also within a facility. Individual prox cards can be programmed with different levels of authorization, so that, for example, inner doors to sensitive areas can be unlocked only by those holding cards with high-level authorization.

HID prox cards often contain identification information as well as access authorization, which allows the smart system to track who opens what doors when, which adds another level of surveillance and security. HID cards can be printed on the outside with identification information as well, making them multi-functional within the workplace.

As a brand, HID cards have a read range up to 24.0 inches or 61 centimeters–except for HID iClass SE type, which have a longer range customized to their specific implementaiton. HID prox cards are contactless, so they eliminate the need for swiping a magnetic stripe, although they also offer a version that includes the magnetic stripe for facilities that have a combination of the two. And while the smart card is the most common form, HID also makes this technology in the form of fobs and tags.

HID Card Access Control

HID Card Types

There are four main HID card types to meet different needs and functions for businesses. While we are just covering the four main categories of HID prox cards, each of these four HID card types has specific subcategories that are further tailored around client needs.

HID Prox Card

iCLASS® Seos

The iClass Seos prox card is one credential that has dual identities, meaning it can be used for physical access and digital access. It can communicate with smartphones and with microprocessors in IT devices. This is the perfect HID proximity card for organizations that deal in IT and digital applications as much as they do locked doors.

iClass Seos credentials can be synced with a smartphone, which allows the smartphone to be read by a compatible reader and act as a smart card itself. They also feature One Time Password technology for two-factor authentication, providing greater security to unlocked IT resources.


iClass SE prox cards are high-frequency to ultra-high-frequency, meaning that the card’s credentials can be read at long range. It is compatible with multiple operations, from outer gates and doors to interior turnstiles and thresholds. This is most useful for large environments like parking garages, or variable environments such as warehouses or manufacturing areas where large machinery is in use, and close access to card readers is difficult or time-consuming.


HID’s iClass specifies high-frequency and high-security cards (though not the HID with the highest security, which is the Crescendo).

This card is also extremely versatile, as it contains contactless, proximity-based, smart-card data chips as well as a magnetic stripe for older readers. It has the widest range of compatible readers, which makes it an ideal access control solution for facilities that have multiple types of readers, as well as those that are in the process of upgrading their access control security system.


The Crescendo, as the name implies, is HID’s most high-powered HID card. Like the iClass Seos, the Crescendo can interface with both physical and digital locks. It uses digital signatures and data encryption to enhance security. The Crescendo 144K FIPS Series is the most secure HID card, with a U.S. NIST (National Institute of Standards and Technology) FIPS 140-2 certification–essential for facilities that must conform to NIST standards by law.

The Crescendo class has a data chip with a larger memory than other HID models, which enables it to record multiple passwords and authorizations.

HIS Crescendo cards are most often used in federal buildings or by contractors that must follow federal guidelines regarding physical and digital security.

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