Integrating Electronics

Electronic access control systems are usually comprised of individual components. Although more and more self-contained products are appearing, there are relatively few "right out of the box" solutions. In every case, whether you are using a "kit" or assembling discrete components, the specification of the system elements, the interfacing with pre-existing site features and the planning of the project are the first and perhaps the most critical step in an installation.

The benefits of self-contained integrated products make them the first choice, assuming that the features properly match your application. A careful assessment of the requirements is necessary to determine if assembling your system from components is a better approach.

Life safety comes first. If using a self-contained standalone in any way compromises the life safety of a door, then it is no longer a candidate, unless it can be augmented with auxiliary equipment. But then, are you defeating the purpose of why you were using the self-contained solution in the first place?

After the life safety issues have been addressed, then the system designer must deal with the rest of the aspects of the project which include:

• What is the objective?
• Is the door an emergency exit or fire door?
• Is the door connected to a perimeter security system?
• Is there existing hardware already on the subject door?
• Is the subject door & existing hardware in good condition?

What is the objective?

Be sure you are listening when the client explains what they want you to install. Often, an installer will have a successful installation using a particular piece of equipment, and then he will try to use the same solution on every project. Unfortunately, if your proposal describes a miracle system that'll do everything, and all the client has been authorized to procure is a simple keypad, you will be immediately suspected of fluffing up the project and you will probably not get the job.

However, if during your visit to survey the site, you notice some security breaches or life safety issues, you definitely should make the client aware of them.

Do not agree to perform work on a door that you think poses a life safety hazard, and perhaps put your concerns in writing with a "decline to bid" letter.

For security breaches, be sure to mention possible solutions as options on your proposal, so that the client will see that you can fulfill their initial request, but also are thoughtful enough to offer your expert opinion for improving on their security posture.

Is the door connected to a perimeter security system?

A perimeter security system on a door poses an interesting set of challenges and possible solutions when adding access control. This is because of the potential for false alarms that could result. Even if the perimeter alarm system is deactivated during normal business hours, the alarm system will most likely be activated at night and on weekends.

An access control system is not a substitute for a perimeter security system. For many applications, the alarm system should be always armed, and the access control system always in service to protect the occupants and assets within.

Most access control systems are installed on premises that do not have full-time security officers or remote video surveillance and door control.

Remote video surveillance, which is gaining popularity because the Internet and networks make it feasible, and remote door control, which involves off-site third parties validating identities then granting access, are still relatively high-end and exotic solutions. Most sites require an automated unmanned process to control access and still maintain security without constant nuisance alarms.

Achieving satisfactory system operation will involve proper interfacing, proper system programming, and proper training of the end-user.

Many times, the locksmith will be called upon to install security on a door where there had been none before, and after there has been a crime. An unauthorized individual enters the premises and takes a purse or a laptop computer. Maybe an estranged spouse shows up for a confrontation, and someone is injured. The employer is not only vulnerable to the loss of assets, but he is also liable for losses and consequential injuries suffered by employees. There is also the very real psychological trauma, loss of productivity and perhaps sudden flight of valuable employees.

These are all issues that you can bring up to your clients if they start to waffle during your presentation. A few thousand dollars sounds like a fortune to a manager until his laptop gets grabbed, and proprietary client information, account histories, and personal files fall into unknown hands. Many companies will not even contemplate outsourcing to a firm unless the firm can demonstrate that it maintains a level of security consistent with the corporate security policy.

When people have been used to behaving in a certain way, there will be a learning curve while they break old habits and develop new ones. There may be a certain degree of recalcitrance on the part of some employees who resist change or authority. Many people are technically challenged, that is, they have trouble dealing with gadgets. They may have a great attitude, but they are slow to adapt to cards, keypads, buttons, flashing lights, etc.

So your mission is to get the hardware to work together, the system to operate and the end-users to be able to get through the door.

• Door Sensor
• Electric Door Strike
• Electromagnetic Lock
• R-E-X Sensor
• R-E-X Station Control
(manually actuated)
• CCTV Camera
• Power Transfer
• Power Supply
• Exit Device
• Keypad or card reader

Door Sensors are devices that are either discrete components, or built into an electric release or electromagnetic lock. The most common type is the magnetic door sensor, which uses a reed switch mounted on the doorjamb and a matching magnet which is mounted on the door. A door sensor monitors the door's position.

Security systems use door sensors that connect to a closed-loop protective circuit (circuit opens when the door is opened.) A device known as an end-of-line resister is frequently used on a protective circuit so that the alarm panel can detect if an attempt is made to short out the wiring going to the door contact, or if the wiring is otherwise damaged. Another type of sensor which provides a closed circuit when the door is opened, but connects to an open loop circuit may also be used, only if an end-of-line resister is used to monitor for loop integrity.


For higher security, latch sensors and status sensors may be used on an opening to confirm that the door is not only closed, but it is also locked and receiving power. When installing an access control system on a door, whether it already on a perimeter alarm, or if the client wishes that the door be monitored will be an important issue for the installer to address. Some access control systems and some alarm control panels are designed to offer this functionality.(See June '02 Locksmith Ledger "Millenium Entry")

But if the door is already on an existing perimeter alarm system, the installer must provide a means to ‘shunt out' the door contact connected to the perimeter alarm system when the subject door is opened by an authorized person, and allow the alarm to be transmitted when the door is forced, left ajar, or perhaps even when someone attempts entry with an expired credential or wrong P.I.N.

A well-designed system is imperative. False alarms have become a contentious issue between the security industry, the police, the municipalities and the public, and excessive nuisance alarms must be avoided.

Selecting an electric door strike begins with determining:
• If the door is an emergency exit which requires a Fail-Safe (Normally Unlocked: unlocks when power is removed or a Fail-Secure: Normally locked but unlocks when the power is applied).
• The correct door release necessary to fit the dimensions of the subject door, the type of lockset on the door and the level of traffic and attack resistance the application requires.
• The correct voltage to operate with the system power supply. Some electric releases are offered with modules that will allow the electric release to be connected with a range of voltages. This is helpful for retrofits, for where there may be voltage drop problems with the installation, or just for the convenience of the installer so fewer different electric releases need to be inventoried. (See July '02 Locksmith Ledger article, ‘Voltage Drop' and January '03 Locksmith Ledger article ‘Why Electric Strikes?')

While we love electromagnetic locks, they are not the solution for every installation (see Locksmith Ledger August 2003 issue for thorough discussion on Electromagnetic Locks)

Short for request to exit, R-E-X sensors, station controls and exit devices are the family of devices used to control egress through a controlled door. Because the Life Safety Code mandates that passage through doors in the path of emergency egress never be impeded, the application of REX devices takes on different philosophies and importance depending on the application.

REX sensors are motion detectors used to sense the presence of a person approaching a door to exit, and ostensibly unlock the door for the person. A motion detector used as a REX sensor should be designed for this application.

REX station controls are devices such as pushbuttons and touch bars which contain switches that are connected into the door control circuit to unlock the door for egress control.

Several motion detection technologies are currently used for REX sensors: PIR (Passive Infrared), Microwave, Photoelectric Beam and combinations of these technologies housed in a single unit to improve performance and reduce false triggering. REX sensors offer a convenience of not having to press button or require manual activation. But they should be used only for convenience and never used as a primary REX device along a path of egress. This is because these sensors must be able to ‘see' a person' before they can signal the door control system, and there are just too many possible ways for a REX motion sensor to fail at a critical moment and create a life safety hazard.


The ways a device can fail are referred to as "Failure Modes." System designers must consider all the possible "Failure Modes" and design their door control systems to take them all into account so that their door control systems will not trap people NO MATTER WHAT HAPPENS.

Besides an arbitrary internal component failure in a REX sensor, vandalism can render it inoperative and the wiring which connects it to the access control system can be damaged somehow preventing egress. If the REX sensor is improperly connected to the access control or the door lock, it might prevent egress. If the building fills with smoke and the REX sensor's view is obstructed, it will not work. There are five ways it can fail.

Not all door control systems are locked from either side and rely on a REX device to allow egress. But any door control system that is connected to an alarm system will benefit from the use of a REX sensor to suppress nuisance alarms. For example, consider a typical door control system using an electric release. If the door is on a perimeter alarm system, the installer can locate a REX button next to the door, put a sign with foot-high letters and flashing lights on it, and building occupants will ignore the button and pass through the door, thereby causing an alarm.

When an electromagnetic lock is used, the issue is much different, because some form of external switch is required to unlock an electromagnetic lock.

Redundant measures must be employed so that the innocent pedestrian has several alternatives to achieve egress, and the system must have built-in methods to ensure that the door will unlock.

An excellent method is the installation and proper connection of a touch bar on the door. There are several types on the market, but the basic concept of an exit bar that one presses on to got through a door is a universally accepted and understood REX control which virtually every person learns from childhood.

Thanks to new technologies, CCTV cameras will continue to find applications and further innovate security management. Cameras already are integral components in entry control and surveillance and motion detection. Future applications will include biometrics and automated entry/exit control systems, among others.

Power Transfer refers to the product group that brings signals, data and power between a moving door and the fixed frame. Common power transfer items are door cords and wired hinges. For installations where equipment may be subjected to vandalism or other damage, concealed-type power transfers such as hinges are preferred.

A power transfer must also have the required number of conductors and current handling ability to match the application.

Power supply is a vital organ in the access control system. A power supply can be as simple as a plug-in wall mount transformer, or as high-tech as a multiple-output, voltage-regulated UL Listed device supplied in a tamper-proof locked enclosure.

Although plug-in "wall warts" can be used and installed in a professional manner to provide reliable power, a plug-in transformer casually plugged into a receptacle selected merely because it is convenient for the installer is not professional practice.

Plug-in power supplies are available in both AC and DC outputs in any voltage you need. Although a plug-in power supply that produces AC voltage is really a transformer, it does after all provide power, so the lexicon of the low-voltage trade has changed to where you can refer to either a device that supplies AC or DC as a power supply. As long as you understand the difference, communicate your specifications accurately and use the appropriately rated device, it boils down to a matter of semantics.

The good part about wall-mounted transformers is that you do not need to be a licensed electrician to install them, and they are usually UL Listed and internally fused or otherwise overload protected so they pose little danger of causing a fire. The bad part is that if you power up your system with something miswired, the power supply may burn itself out and you have to replace it.

Another possible shortcoming is that if your power supply is operated in a critical region of its output rating, there may be a thermal cutoff built into the device which will occasionally interrupt power to your system, or the thermal cutoff may fail.

If plug-in power supplies are used, they should be mounted in locations where they cannot be accidentally kicked out of the outlet, or otherwise be readily unplugged and where people cannot trip over the wire.

In addition, make sure the breaker feeding the receptacle is properly rated, appropriately labeled and other non-security equipment does not share the branch circuit. The receptacle should not be on a wall switch, timer or other power management system.

Wall-mount power supplies are available with visual indicators (pilot light or LED) indicating they are "ON." If this feature prevents just ONE unnecessary service call, you've saved yourself a quick 50 bucks. Power supplies can provide all the voltages needed for the entire access control system, the lock, the reader, any illuminated devices; wire connection points (a terminal strip) to connect the system to the building fire alarm; and battery backup to keep the system running in the event of a power failure.

Good access system design provides for adequate power available at each door location. This is sometimes accomplished with separate ‘satellite' power supplies installed at each door or in a location convenient to a group of doors, or by a master power supply located at a central location. The labor involved in hauling wire, and the voltage drop excessively long wire runs may cause, are factors which will affect the technique a designer will select for a particular project.