Purpose of Door Alarm Monitoring

 

Most businesses and organizations use some form of card access control system to control entry into their buildings and other facilities. These systems allow authorized employees to conveniently enter through secured doors without needing to use a key.

 

In addition to controlling access, most card access control systems also provide a door alarm monitoring feature. The purpose of door alarm monitoring is to detect improper use of the card access controlled door. Two types of door monitoring are commonly provided:

 

"Door-Forced-Open" Monitoring

 

In the event that any card reader door is opened from outside without the use of a valid access card, the system will cause a "Door-Forced-Open" (DFO) condition to occur. For example, if an intruder were to pry the door open from the outside, this would cause a DFO condition to occur.

 

"Door-Open-Too-Long" Monitoring

 

In the event that any card reader door is propped or held open, the system will cause a "Door-Open-Too-Long" (OTL) condition to occur. For example, if an employee were to wedge a door open, this would cause a OTL condition to occur.

 

In most cases, the access control system is designed so that a security monitoring center is notified whenever a DFO or OTL condition occurs, allowing an appropriate security response to be made. In some cases this may involve dispatching a security officer to the door to investigate; in other cases, an employee working near the door may be called and asked to see what is going on at the door. If the facility has a video surveillance system, the monitoring center may also use a video camera to observe activity at the door.

 

The door alarm monitoring feature is a necessary part of any automated security system. It makes no sense to install an expensive card access control system if doors can be opened without using an access card, or if people can walk in freely through doors that have been propped open. When working correctly, the door monitoring feature greatly improves security and provides assurance that all doors are being used as intended.

 

The Problem

 

Unfortunately, the door alarm monitoring feature is a major source of of grief at many facilities. The problem: false DFO alarms. In most cases, these false alarms occur even though employees have done nothing wrong; they simply used the access controlled door in normal manner, yet the system triggered a false DFO alarm. In larger facilities, this can occur hundreds or even thousands of times per day. These alarms can flood the security monitoring center, overwhelming the monitoring staff.

 

Eventually, monitoring staff may become complacent about DFO alarms, or choose to ignore them completely. At some facilities, false DFO alarms can be such a problem that management becomes frustrated, and chooses to permanently disable the door alarm monitoring feature. Neither of these responses is appropriate as they decrease the overall level of security at the facility and turn the access control system into just an electronic locking system.

 

Is There a Solution?

 

Many end-users (and even security systems integrators) have come to accept the false DFO problem as unsolvable. These people have given up on trying to find a solution and consider false DFO alarms to be a fact of life when using a access control system.

 

Is there a solution? Yes! While false DFO alarms can never be entirely eliminated, Silva Consultants believes that they can be reduced by 95% or more through effective system design.

 

At facilities that already have systems installed, modifications can be made to existing equipment that will eliminate most false DFO alarms. Fixing false DFO problems on existing systems requires work, but can be done with some knowledge of basic design principles and a little patience.

 

How Door Monitoring Works

 

Before discussing specific solutions to the false DFO problem, it is helpful to understand how the door monitoring feature works on the typical access control system.

 

The typical access controlled door has the following devices:

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• Card reader on outside (non-secured) side of door. Common types of card readers include proximity readers, smartcard readers, and magnetic stripe readers.

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• Request-to-exit (REX) device on inside (secured) side of door. Common types of REX devices include REX motion detectors, REX switches in lock hardware, and manual REX buttons.

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• Electric lock hardware. Common types of electric lock hardware include electric strikes, electric locks, and electromagnetic locks.

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• Door position switch. The most common type of door position switch is the magnetic contact switch.

 

All of the devices at the door are connected to the access control system, usually through some type of intelligent control panel which may be located at the door, or in a nearby electrical closet.

 

Here is how the access control system door monitoring feature works:

 

Entering through the door from the outside:

 

When a user presents his or her card at the card reader, the reader sends a signal to the access control system. If the card is valid, the access control systems sends a signal back to the electric lock hardware, causing the door to unlock. As the user opens the door, the door position switch sends a signal to the access control system, but because a valid card has just been used at the reader, the access control system does not cause a DFO alarm to occur.

 

Exiting through the door from the inside:

 

When a user approaches the door to exit, he or she activates the REX device. In the case of a REX motion detector, this occurs when the user steps into the detector's coverage area. In the case of a REX switch inside of hardware, this occurs when the user turns the door handle or presses the exit bar. When using a manual REX button, this occurs when the user presses the button to leave. As the user opens the door, the door position switch sends a signal to the access control system, but because a REX device was just activated, the access control system does not cause a DFO alarm to occur.

 

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.

 

So, in summary, if a door is opened without using either the card reader or activating a REX device, a DFO alarm will occur.

 

Common Causes of False DFO Alarms

 

The following are some common causes of false DFO alarms:

 

Improper REX Motion Detector Coverage

 

REX motion detectors need to detect people just as they are ready to open the door. Too often, REX motion detectors are placed where they detect people approaching the door rather than at the door itself. This is sometimes done with good intentions ("I will detect them long before they get to the door") but can create a "blind spot" in front of the door itself. (See Figure #1 below).

 

Users can pass through the detector's coverage area and pause before opening the door, often long enough to allow the REX detector to reset. The user then opens the door, causing a DFO alarm to occur.