Access Control System
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
  3. Locking Device
  4. Door Position Switch
  5. Request to Exit Device
  6. Controller
  7. User Interface (Software)
Credentials are typically the familiar access card 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 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. Simply push the button to activate a relay, and the gate or door opens on command.

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.