ACCESS CONTROL SYSTEMS

Nationwide Security Corporation designs access control systems that provide the essential services of identification and authentication. As a credential such as a personal access number or key card is presented to a reader, the system determines if the individual is allowed to access the building.

There are many card technologies including magnetic stripe, bar code, proximity cards, and smart cards. Typical biometric technologies include fingerprint, facial recognition, iris recognition, retinal scan, voice scan, and hand geometry are also available.

Access control points can be a door, turnstile, parking gate, elevator, or  anyother physical barrier placed where access needs to be controlled.   An electronic access control door can contain several elements.  At its most basic there is a stand-alone electronic lock.  In larger applications involving more than one door electric strikes or magnetic locks are used.

Generally, entry is controlled and exit is uncontrolled.  In cases where exit is also controlled, a second reader is used on the opposite side of the door. In cases where exit is not controlled - free exit - a device called a request-to-exit (REX) is used. Request-to-exit devices can be a pushbutton or a motion detector. When the button is pushed or the motion detector detects motion at the door, the door alarm is temporarily ignored while the door is opened. Exiting a door without having to electrically unlock the door is called mechanical free egress.  This is an important safety feature.  In cases where the lock must be electrically unlocked on exit, the request-to-exit device also unlocks the door.

Types of readers:
Access control readers may be classified by the functions they are able to perform:

Basic (non-intelligent) readers: simply read card number or PIN and forward it to a control panel. In case of biometric identification, such readers output ID number of a user.

Semi-intelligent readers: have all inputs and outputs necessary to control door hardware (lock, door contact, exit button), but do not make any access decisions. When a user presents a card or enters PIN, the reader sends information to the main controller and waits for its response. If the connection to the main controller is interrupted, the readers stop working or function in a degraded mode. Usually semi-intelligent readers are connected to a control panel via an RS-485 bus.

Intelligent readers: have all inputs and outputs necessary to control door hardware. They also have memory and processing power necessary to make access decisions independently. They are connected to a control panel the same way as semi-intelligent readers, via an RS-485 bus. The control panel sends configuration updates and retrieves events from the readers. There is also a new generation of intelligent readers referred to as "IP readers". Systems with IP readers usually do not have traditional control panels and readers communicate directly to PC that acts as a host.

Serial controllers:
Controllers are connected to a host PC via a serial RS-485 communication line. External RS-232/485 converters or internal RS-485 cards have to be installed as standard PCs do not have RS-485 communication ports. In larger systems multi-port serial IO boards are used. High reliability and security as the communication line is not shared with any other systems.

Serial main and sub-controllers:
All door hardware is connected to sub-controllers (a.k.a. door controllers or door interfaces). Sub-controllers usually do not make access decisions, and forward all requests to the main controllers. Main controllers usually support from 16 to 32 sub-controllers

Serial main controllers & intelligent readers:
All door hardware is connected directly to intelligent or semi-intelligent readers. Readers usually do not make access decisions, and forward all requests to the main controller. Only when the connection to the main controller is unavailable do the readers use their internal database to make access decisions and record events. Semi-intelligent reader that have no database and cannot function without the main controller should be used only in areas that do not require high security.

Serial controllers with terminal servers:
In spite of the rapid development and increasing use of computer networks, access control manufacturers remained conservative and did not rush to introduce network-enabled products. When pressed for solutions with network connectivity, many chose the option requiring less effort: addition of a terminal server, a device that converts serial data for transmission via LAN or WAN.

• Allows utilizing existing network infrastructure for connecting separate segments of the system.
• Provides convenient solution in cases when installation of an RS-485 line would be difficult or impossible.