The Basics of Access Control
By Byron Hedahl*
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?
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
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
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
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
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
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
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 www.UL325.com.
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.
This article reprinted from
Professional Door Dealer