By Scott Lindley
Electronic access control systems offer several advantages over traditional locks and keys. Badges, tokens, or cards limit access to a facility to only individuals with these devices. For example, companies can restrict employees access to certain areas, or program security systems to limit access to only specific times (i.e. few hours before and after a scheduled event for vendors or delivery people).
Often, when one starts exploring the world of keyless access, a new series of terms arise—passive cards, active cards, proximity cards, smart cards, long-range readers, and Wiegand. This article provides an overview of these access control technologies and how they fit into a building’s security systems.
Passive and active cards
Passive and active readers are the two older technologies. Powered by radio frequency (RF), signals from a passive card reader have a limited range of 101 mm (4 in.) and must be held close to the user. It does not have its own battery. The larger the RF, the longer it will read in distance. Devices mounted on walls are typically rectangular or square, while other readers are designed to fit on a mullion, door, or screen. The passive card and reader communicate with each other by an RF process called resonant energy coupling.
Passive cards have three internal components—antenna, capacitor, and integrated circuit—to store the user’s ID number and other data. The reader also has an antenna generating a short-range RF field in a spherical orbit. When the card is placed within range of the reader, the card’s antenna and capacitor absorb and store energy from the field and resonate. This powers the integrated circuit, which sends the ID number to the card’s antenna, transmitted by RF signals back to the reader.
Powered by an internal lithium battery, some devices can produce a much longer read range than passive card technologies. An active card reader’s integrated circuit contains a receiver and transmitter using the battery’s power to amplify the signal so active cards can be detected from long distances. However, the longer read ranges and spherical orbit can create problems, such as when several card readers and reads end up conversing with each other, creating a sort of communication ‘mayhem.’ Users should pick a card that works best with the application and with the right type of reader.
Proximity cards and Wiegand standards constitute the majority of card-based keyless access. With these 125-KHz devices, there is no contact between cards and the reader, eliminating the wear-and-tear. Further, the reader is often durable or hidden into the wall so it cannot be vandalized. In some cases, the device may even withstand a ballistic attack.
The card readers communicate to the rest of the access control systems in various protocols, such as Wiegand—a wiring standard that arose in the 1980s. Another popular protocol is a standard magnetic stripe card interface. When selecting a proximity card and reader, there are factors to keep in mind. It needs to comply with its interface protocols so cards and readers will work with a wide range of electronic access control systems. It is important to check to see if the reader electronics are secured with tamper- and weather-resistant epoxy potting, in the event the device is used outdoors or in wet or dusty environments. The electronics should have a lifetime warranty. Business-owners may also want a multi-factor verification system in addition to a card to activate the door lock (e.g. card keypad reader).
Contactless smart cards are expected to surpass proximity cards in the next few years. These 13.56-MHz smart card systems are securer and used for applications beyond access control (e.g. tool checkouts, or purchases at a company cafeteria). They conform to International Organization for Standardization (ISO) standards. The identification cards operate within 101 mm (4 in.), ensuring a positive read and comfort for the user. However, it is important to note proprietary, non-standard-based smart card technologies could bind a user to a single-supplier dependency and potentially restrictive pricing and delivery structures.
In addition, the Open Supervised Device Protocol (OSDP) helps ensure numerous manufacturers’ products will work with each other. Interoperability can be achieved regardless of system architecture. The specification handles smart cards, constantly monitoring wiring to protect against attacks and serves as a solution for high-end encryption as required in federal applications. The specification for handling light-emitting diodes (LEDs), text, buzzers and other feedback mechanisms provides a rich, user-centric access control environment.
Smart card readers have many of the same features found in proximity card readers—potted, different sizes, and card plus keypad.