Friday, July 18, 2008

Access Control System Basics

The Basics of access control

While access control has been around for centuries in one form or another, it has only been in the last several decades that it has moved beyond the basics.
Access control can be defined as, “A system that allows the right person into the right place at the right time.” This principle holds true in all industries and applications. This article will explain the basics of access control in relation to the gate and door industry, sometimes referred to as “perimeter-access areas.”

Layout and Design
As with any project, the initial step is to develop a good idea of what the needs are and how they can best be met. Every perimeter-access area will be different, but some questions will always need to be asked:
How many access points are needed?
How often are the access points used?
Should the access points be linked together via a wired/wireless network, or would individual, stand-alone controls work better?
How many individual users will need to use the system?
How secure does the facility need to be?
What type of gate/door controller should be used?
What type of entry device (keypad, card reader, voice communication, etc.) should be used?
Product Selection

One of the key components of the design process is product selection. For example, a customer may know he would like to use a proximity card reader to control entry because he wants a more secure facility. He then needs to consider whether he would like a short-range reader, long-range reader or even an automobile tagging system. Or perhaps the customer would like to have two gate operators installed, one on a steep hill, and another between two buildings with no room for a gate to maneuver. He needs to know which product options are available.

Perimeter access-control equipment can be categorized into several different groups: entry/exit devices, gate/door operators and safety devices. Here’s a breakdown of each.

Entry/Exit devices Pushbuttons/ Key-switches—These are the most archaic of all access-control devices, yet they are still being used in large numbers. Simply push the button or turn a key to activate a relay, and the gate or door opens on command. These are not very secure, but easy to install and use.

Keypads—Keypads are probably the most common entry device for access control. They are very simple to use, but provide a higher level of security than just a pushbutton. However, once a code is given out, the system’s security is breached. Keypads come in interior and exterior configurations, so finding the right one is a simple process.

Card Readers—The most commonly one used for access control is the proximity card reader. Simply pass a card through a special radio field, and all information on the card is read, allowing access. Proximity range can vary from 1 inch up to 3 feet, depending on the system. Other card reader systems include touch-plate, magnetic common code, mag-stripe and barcode.

Voice Communication—Whether it be a simple intercom or a complex telephone-entry system, voice communication is an integral part of many access-control systems. The intercom systems are generally very basic, allowing connections throughout the building. Telephone-entry systems come in two varieties: 1) a residential unit that uses the existing telephone line to ring all of the phones in the house; or 2) a system that needs its own telephone line so it can actually dial an extension, apartment or completely different house.

Sensors/Probes—While these units are also often used as safety devices, they provide the dual purpose of allowing a vehicle to exit a property. A loop detector, photo cell/beam or probe—all of which work by detecting a large metal mass such as a vehicle—is placed in the exit lane of a property. When the vehicle drives over or past it, the gate will open, giving the vehicle a free exit.

Radio Transmitters/Receivers
These are almost identical to a garage door transmitter, except they work on a separate receiver for the gate/door. In fact, there are several companies that manufacture dual-button devices to work on gates and doors. This is one of the most commonly used types of access control for gates.

Automobile Tags—These tags are usually placed on the windshield. As soon as the vehicle is within range of the reader (between 6 and 450 feet), the receiver recognizes the tag on the vehicle and the gate opens.

Mag locks/Electric strikes—Both of these devices are used to hold the gate/door closed until an entry/exit device is triggered.

Slide Gate Operators—These are commonly used in commercial applications. The units require additional room to slide back along the fence line, so when space is limited, slide gates may not work. However, they work very well in areas where snow or wind is a concern.

Swing Gate Operators—These units are used in residential applications quite frequently, as well as areas where slide gates are not feasible. Because swing gates take more time to open and close and require much more room to open than slide gates, they are ideal for situations where constant use is not a concern. They are difficult to use in areas where snow and high wind are problems.

Actuators—These are actually a form of swing gate operator; however, they are used almost exclusively for residential/small-commercial gate applications due to the restrictions based on their small size. They can only handle smaller, lighter gates and usually have a limit on the number of cycles per hour they can work.

Barrier Arms—Most often used in parking applications, these operators don’t provide much security, but allow for controlling the entry/exit or movement of vehicles in a facility. Arms can be varying lengths and can be made of wood, metal or plastic.

Vertical Pivots—These are likely the most expensive of the listed operators because they are required to do more work. They lift the gate completely off the ground, 90 degrees into the air. All units are also counter-balanced so if a problem occurs with the operator, the gate can still be raised manually.

Overhead Door Operators—As the name implies, these are designed to open overhead doors and are basically commercial versions of garage door operators. There are two main types: trolley and jackshaft. Trolley operators have the motor unit mounted above, between and behind the horizontal rail tracks. The trolley thus provides constant contact with the door and is suitable for areas with low ceilings where the door cannot raise vertically. Jackshaft operators are mounted to the side of the door and connected to the shaft with a drive chain.

Loop Detectors/Sensors—As mentioned previously, these units function by detecting a large mass of metal. As a gate or door is closing, if a mass of metal is detected entering the area of the gate or door, the detector/sensor will reverse the unit, allowing the vehicle to pass through unharmed.

Photo Cells/Beams—These devices will reverse the gate/door exactly as a detector or sensor will, except they work with a beam of light. When the beam is broken by a vehicle, pedestrian, or even a pet, the door or gate will reverse.

Safety Edges—A good failsafe to have on any door or gate is a safety edge. With a loop detector or photo cell installed, usually the gate or door will reverse. But what happens if one of those items is damaged for some reason? A safety edge can be installed along the leading edge of the door/gate that will detect a slight increase in pressure if it comes in contact with a vehicle, pedestrian or even a pet, etc., and cause the door or gate to automatically reverse.
INSTALLATION Once access-control equipment has been chosen, careful consideration should be given to how that equipment will work together. Are there enough wires running to each location for communication, or will a wireless network need to be established? Is there accessible power for each system, or will one need to be changed to a solarpowered system? Here are a few points to consider when installing the equipment.

Wired vs. Wireless—Almost all applications for access control require a wired connection between access-control devices. A radio receiver may have wireless transmitters, but it must still be hardwired to the gate operator. There are, though, several units available that allow for a wireless transmission of data. However, line of sight is usually a requirement. Also, interference from other radio transmissions may cause temporary loss of signal, resulting in a nonfunctioning access-control device.

Residential vs. Commercial—Many times, a manufacturer will offer two versions of its access-control equipment, one for residential applications and another for commercial. Commercial equipment is much heavier duty, can handle more use, and has more features than residential equipment, making it more expensive. Also, commercial installations usually require additional safety equipment that may not be required on residential applications.

AC vs. Solar Power—Most solar applications are for residential and farm use, while many commercial applications still use AC equipment in lieu of solar. However, that is beginning to change as solar technology improves. Look for more manufacturers to begin making constant-cycle/constant-duty equipment that can be powered entirely by solar energy.

Wiegand Devices—Wiegand signals are used almost exclusively in access controls and are extremely common in the gate/door industry. The maximum distance the Wiegand signal will travel over wire is 500 feet, which will effect how systems can communicate with each other.
UL 325 Standards—The issue of personal safety is triggering many changes in the access-control industry. As with many mechanical devices, there is the potential of malfunction or human error leading to injury or even death. Compound that with legal liability, and it becomes a very hot subject that the industry has, unfortunately, had to deal with in the recent past.
In an effort to regulate and set standards for the design, manufacture and installation of automatic gates, a set of regulations has been developed known as “UL 325.” Although many of the UL325 standards are currently voluntary, this is quickly changing as local municipalities are requiring these standards to be met. Every person who works with access-control equipment should be familiar with these standards. A good review of the standard can be found at
Overall, the access-control industry can seem quite intimidating with its many standards and new technology, but it is important to remember that it is really very simple. Just like flipping a light switch turns on a light, so too does a keypad, card reader, or sensor simply open a gate or door. By using all available resources, such as manufacturers’ reps, the Internet and other industry professionals, access control can quickly become much less daunting.

No comments: