Doors, locks, cards, and readers are the most obvious physical components of an access control system, but other key hardware is less obvious. This piece explains the function of each component of an access control system.
10 Hardware Components of Electronic Access Control Systems
The children’s joke goes “When is a door not a door? When it’s ajar.” In that silly play on words resides a profound truth. A door ceases its access control function when it is not closed and secured. Doors remain the linchpin of access control.
Doors can be classified by the material with which they are constructed. They include steel, fiberglass, wood, aluminum, and glass.
Most steel doors are durable and secure. Since steel is common and relatively inexpensive, this door type is commonly used in office and industrial envrionments.
Fiberglass doors are extremely durable and long lasting. They are also a popular choice for electronic access control in commercial settings.
Wood doors are inexpensive but not secure. They are often used for interior office doors because they are not durable and erode in harsh weather.
Aluminum doors, which often include panes of glass, offer a sleek, upscale look to offices. Glass panels allow users to see who is on the other side of the door. When safety glass is used, aluminum doors can be durable and secure.
Glass doors create the sense of open space and are ideal for open offices. They maximize natural light and project transparency and modernity. For safety’s sake, many companies opt for special security glass or coatings.
Retrofitting glass doors for electronic access control may mean compromising aesthetics. Solutions that combine security with beauty include wireless readers and electromechanical locks mounted at the top of the door frame.
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Door Locks in Access Control
The most common types of locks used in electronic access control are electromagnetic locks and electric strike locks.
These locks consist of an electromagnet attached to the top of a door frame and an armature plate (that is, a plate to which a magnet sticks) attached to the door. As an article by Allegion describes, “Magnetic locks use electromagnetism to control the entire locking mechanism. When the magnet is energized, it bonds to the armature and locks the door. To allow access or egress, a switch must be provided to de-energize the magnet. As the electric power activates the magnet, the bolt locks the door. To unlock the door, simply remove power.”
Unlike electric strikes, magnetic locks keep the door locked from both sides. They are fast-working and durable, thus suitable for high-traffic areas. However, they can be defeated by cutting the power supply. They can also be difficult to install because they are mounted in the frame, requiring that wiring go inside the frame.
Electric Strike Locks
So-called “electric strikes” are mechanical locks that use electronic components. According to a blog post by Koorsen Fire and Security, “Electric strikes are used in combination with another form of locking devices, such as a lock set or a panic bar. They are installed in place of the conventional lock strike plate on the inside of the door frame. Electrical power is supplied to the strike, which holds the latch or lock bolt in place, keeping the door locked until the release system is activated.” Generally, these locks are one-way only. They are easy to install because they are mounted on the face of the door and frame.
Request to Exit Devices in Access Control
Request to Exit (REX) devices allow people within an access controlled area to exit the space without having to use a credential, keypad, or other means. Typically, either a motion detector will register someone approaching the door and automatically release the lock, or the person will push a button or turn a door handle that releases the lock.
As explained in a post by Silva Consultants, “If an access controlled door is opened without either the use of a valid access card or the activation of a REX device, a door-forced-open (DFO) alarm will occur. This occurs because the access control system has received a signal from the door position switch telling it that the door has been opened, and without having received a previous signal from either the card reader or REX device, it assumes that the door is being forced open.”
REX devices almost always use infrared technology for their sensors. Passive infrared sensors detect heat and unlock the door in response to change in temperature. They are passive because they only receive only the infrared signal (i.e. heat). More sophisticated PIRs detect both heat and motion, which makes them harder to spoof. For example, a well-known way of entering a locked door that has a change-of-heat-triggered REX on the other side is to spray an upside-down can of compressed air with a narrow straw in the gap between the door and the frame. The change in temperature unlocks the door.
Active infrared sensors have both an emitter and a receiver. If the sensor beam is broken by an object, such as a person, it triggers the door to unlock.
Access Control Readers
Access control readers do just what they describe. Installed at protected access points, they “read” some input, such as a card, a face, a mobile phone, or a signature, and they forward the information to a control panel, often using the Wiegand protocol. In the case of cards, almost all systems work through proximity detection of a signal or by swipe. So-called “dumb” readers stop there.
Semi-intelligent readers transfer the data to the main controller/panel and await a response. If the input is approved, these readers trigger the door to unlock.
Intelligent readers have the processing power to make the access decisions themselves and trigger the door to unlock. They pass information to the controller/panel not for the latter to make access decisions, but to store transactional data. The only information that goes from controller/panel to reader is configuration and access updates.
Keypads serve a similar purpose as readers. They receive an input that enables a user to enter a controlled space. Keypads are often configured like telephone keys. The door unlocks when a user punches in the correct sequence of numbers, letters, or characters.
In electronic access control, keypads can be standalone systems, feeding into a separate access control server, or they can integrate with key card-based, biometric, or other access control systems. Easy to install, they are often used as backups for card or biometric-based systems.
However, users can easily share passcodes, and adversaries can learn a code by watching an authorized user at the keypad. Plus, keypads don’t produce an audit trail because everyone uses the same number. Thus they are best as backups or for low-security installations.
Access Control Panels/Controllers
Access control panels, otherwise known as field panels or controllers, are the hidden workhorses of access control systems. Often located in telephone or electrical closets, access control panels pull together all of the hardware. They connect to readers, REX devices, other sensors, locks, and related hardware, processing all access control activity. As the muscles of the system, they take orders from and report into the central access control server.
The number of panels in a facility depends on the numbers of doors covered. Each panel accommodates up to 10 doors.
If panels are the muscle of an access control system, then servers are the brains. The software assigns access to and tracks traffic through access points. Besides holding a database of authorized users and their access levels, it retrieves access control data from each panel.
Cables and Wiring
Many access control systems, especially legacy systems, rely on cables to transport data. It’s much like how humans use their nervous systems to convey information back and forth between the brain and individual body parts. Even wireless systems often use some wiring, such as in legacy readers.
IPVM’s cabling guide describes the type of wiring used for each connection. Reader wire (6-8 conductor cable) connects readers to panels. Controller wire (Ethernet or 4-pair untwisted pair) connects the main control panel with field panels and can run thousands of feet. Lock & DPS wire delivers power to maglocks, electric strikes, and other accessory devices. Shielding wires help drain interfering signals and preserve the integrity of communications between reader and panel.
Access Control Power Supply
Access control systems often require their own power supply. These help reduce the power delivered from the electric utility (e.g. 120 volts AC in the United States) to a form that an access control system can accommodate. Most systems run on 12 volts DC, though others run on 24.
The two common types of power are linear and switch mode. Linear systems are like small transformers and can run hot. Switch mode power supplies are smaller, lighter, and run cooler. However they emit high-pitched noises that can interfere with sensitive electronic equipment.
The components described above comprise the basic hardware of access control systems. Many other components and accessories exist, such as door alarms, backup batteries, cameras, intercoms, and turnstiles. But every system starts with the basics.