The Basic Access Control System

Page content

Access Control Functions

As we discussed in the previous article of this series, the basic function of any access control system is to deny and/or grant access into a commercial, industrial, or governmental structure or facility. There are four processes that every access control system must employ to be effective in its purpose. These are: Identification, Authentication, Authorization, and Accountability. The Identification process gathers information about who is requesting access. Authentication is accomplished by methods designed to prove or disprove the Identification information. Authorization consists of a set of rules that define who can enter and under what circumstances. Finally, Accountability is the process of logging and reporting not only who has requested access and the results of that request, but also who has created the Authorization rules that were applied.

System Components

The basic components of any access control system are:

  1. Credential

  2. Reader or Keypad

  3. Locking Device

  4. Door Position Switch

  1. Request to Exit Device (REX)

  2. Controller

  3. User Interface (Software)

Each of these components will be examined at greater length in subsequent articles of this series. For this review of the basic system components a simple description and application of each component will suffice.

Credentials are typically the familiar access card but can also include a personal identification number (PIN) or a biometric such as a finger print, hand geometry, or iris pattern. Whatever credential is used, it serves as a method by which identification of an individual is presented to the system for authentication.

A reader or keypad is used to receive the information presented by the credential. Most common is the proximity card reader whereby an access card is presented to within a few inches of the reader so that the reader can read the identification information from the access card. The identification information, or card number, is sent upstream to the controller for processing.

Locking devices are electrified locks, electric strikes, or even electromagnetic devices; all designed to hold a door closed until such time that the controller has authenticated the identification information presented via the credential and determined that the circumstances warrant authorization to access a door or gate.

A door position switch keeps the system apprised as to the status, open or closed, of the entry point at all times. Without this sometimes neglected device the access system will never know if the door has been propped open.

Request-to-exit devices are used to alert the system to the fact that someone is about to egress the secured area. This information is necessary to differentiate between a door forced open alarm condition and a routine egress opening.

The controller is the intelligence of the system. All access decisions are made by the controller. The controller firmware and database make every decision and remember every user. A well designed access system will distribute all intelligence throughout the controllers in the system such that the system does not rely on the user interface software for routine operation.

The user interface is software that is used for human interaction with the access system. Software can include simple set up and reporting commands or very sophisticated graphical representations of a building with device icons, alarm indications, and even live video feeds. Regardless of the complexity of the software, its purpose is to allow people to input information, create authorization rules, and review accountability information about the system.


Whether an access control system is deployed to protect a global enterprise with thousands of doors and gates or an SMB (Small-Medium Business) with just a few doors and a few employees, the system components and their function within the system remain the same. Both employ the same processes and differ only in scale. Today’s access control systems often include very sophisticated features and integrate with other security systems, but essentially provide the same service of letting the right people through the right doors at the right time.

This post is part of the series: A comprehensive Review of Electronic Access Control Systems

From the basics of what it is and why we need it to the intricacies of enterprise class integrated security systems, this series will discuss access control in a format that will bring the electronic security neophyte up to speed quickly and yet enlighten the seasoned industry practitioner.

  1. Access Control - What is it and Why we Need It
  2. Access Control Systems: The Basics