Access Control

Access Control System Operation

Sometimes the best way to understand a system is to walk through a typical use of the system. In access control this typically begins when the user presents the assigned credential to the appropriate reader. The reader conveys the credential’s information to the device that makes the access decision. In most electronic access control systems this is a highly reliable independent control panel. The control panel is aware of the current time and date and decides whether the holder of the presented credential is allowed access at this door at this time and date. Whether access is granted or denied, the transaction is recorded providing a history that can be consulted when questions arise about who was in the protected area.

Access Control System Components

An access control point can be a door, turnstile, parking gate, elevator, or other physical barrier where the granting of access can be electrically controlled. Typically the access point is a door and the access is controlled through either a magnetic lock or electric strike.

Knowing the position of the door is an important element of the system and is typically accomplished with a magnetic switch concealed in the frame of the door. This sensor is used to detect a door forced open without authorization or being held open too long after authorization. Sometimes there are additional sensors that monitor the state of the lock, motion in the protected area, and other alarm sensors.

The user’s primary interface with an access control system is the credential reader. A reader reflects the technology of the credential. The reader for a magnetic stripe, bar code, or Wiegand card is typically called a swipe reader and is in common use in retail stores and ATMs. Some swipe readers require the card to be swiped in a specific direction in order to get a good read, but the typical swipe reader for access control can read the credential when it is swiped in either direction. The reader for a proximity or contactless smart card is actually a radio transceiver. The broadcast field of the reader activates the card, which then begins radio-based transaction with the reader. The smart cards with the gold contacts visible on the front of the card are known as contact smart cards and require the gold contacts to physically touch contacts on the reader to accomplish the transaction. Biometric readers are unique to the technology being used but always require the users to present some part of their body, whether it is actually touching the reader for fingerprint or hand geometry or looking at a camera in the case of face recognition, iris and retinal scanning or speaking into a microphone in the case of voice recognition.

Entry into a protected area always requires a device to validate the person requesting access. Exit from a protected area may or may not require validation. When it does, a second reader, almost always using the same technology as entry validation, is used for exit validation. Even when exit validation is desired, fire and emergency codes require a means of exiting an area without validation. For that purpose there are a range of “Request to Exit” devices commonly called REX devices. A REX device may be as simple as a pushbutton or as sophisticated as a heat and motion detector. In any case the REX button will unlock the door for at least as long as the REX device is activated. If exit validation is not required, REX activation is considered normal operation. If exit validation is required, activation of the REX device may trigger an alarm.

Each of the above devices is connected to an access control panel. This panel should be designed to operate standalone, in the absence of any supervising computer. The control device must have backup power capable of sustaining the operation of the system during a primary power failure for as long as it typically takes to re-establish primary power or make arrangements for an alternate power source. The access control panel must also detect and generate an alarm any time the control enclosure is opened so that a monitoring guard is aware of any attempts at tampering with the system.

Summary

Electronic access control systems today range from standalone single door controllers to complex networked systems integrated with closed circuit television systems, burglar alarm systems, and other building control systems. The selection of the proper credentials and readers, the system features needed, and the many choices available for installation and implementation can require complex planning and difficult decisions. There are books available to help you learn more about these choices or you can contact a professional dealer to help you define your needs and arrive at an appropriate solution. If you would like to begin the process of defining your needs, try taking our free risk analysis.

Credential

A credential is something you have, something you know, some biological characteristic, or some combination of these. The typical credential today is something you have such as an access card, key fob, or other key. There are many card technologies including magnetic stripe, bar code, Wiegand, 125 kHz proximity, contact smart cards, and contactless smart cards. A credential based on something you know can be a Personal Identification Number (PIN), a combination, or a password. The use of biological characteristics as credentials is generally called biometrics. Typical biometric technologies include fingerprint, face recognition, iris recognition, retinal scan, voice, and hand geometry. All card technologies are generally used to convey an identification number that is comprised of three components: the card number, the facility or site code, and the issue number. The card number is a unique number that distinguishes the cardholder from all other cardholders. The facility code, also called the site code, is a number that was created, when memory was expensive, to allow the range of unique numbers to be smaller while eliminating duplicate numbers. The issue number is incremented each time the card is replaced due to a lost or missing card.

The identification number in most card technologies is generally stored in one of two formats: Wiegand or ABA. The Wiegand format, named for the card technology where the format was first used is bit-oriented and ranges from 26 to 60 bits long. The ABA format, named for the American Banking Association, is digit oriented and is typically found on credit cards or other cards using magnetic stripe technology.