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Silencing false alarms.

THE PROBLEMS ASSOCIATED WITH false alarms have received considerable attention lately--in the media, in legislation at the state and local levels, and by law enforcement officials who must respond to the alarms. Just what constitutes a false or nuisance alarm, and how can they be avoided?

A false alarm is anything that affects the electronics of the system or the transmission lines. A nuisance alarm is any sensor response to unintentional stimuli.

False and nuisance alarms can be controlled. If your company wants to install an alarm system, a number of factors need to be considered. For starters, companies must follow a few common sense basics. Equipment must be reliable, affordable, available, maintainable, and expandable.

Consider the hourly maintenance charges for service when the system is out of warranty and whether you can afford the repairs. Determine whether the system can be retrofitted if newer technology comes along.

You need to have confidence in your system and be well trained in its functions and operation. Your training should include a list of do's and don'ts, which can go a long way toward eliminating false and nuisance alarms.

In addition, ensuring that a site has been carefully examined and prepared is crucial to the successful operation of an alarm system. In installing alarm systems--whether industrial, commercial, or residential--half the technical battle is won with a thorough site survey. A site survey includes looking at environmental factors as well as testing for the effects of inductive, conductive, and radiative interference.

Site preparation is far more complex and comprehensive than many clients realize. A site survey involves asking a lot of questions. It also means the people who are responsible for the system's design must work closely with the installers before and during the installation.

As a client, you should ask yourself many of the same questions the installer needs to know. For example, in what type of environment will the alarm system be placed and expected to operate efficiently?

What is the condition of the building's electrical system? This includes the building's transformers and switchboards; bonding and grounding networks; circuit-breaker panels, switches, and receptacles; and all of the wiring in between.

Electrical noise from one part of the building can travel through the building's wiring and interfere with or damage electronic equipment. Loose connections, in addition to causing voltage and current losses, can cause electrical noise.

The majority of sites I have visited had incorrectly wired AC receptacles and were using light-duty use residential grade receptacles. Connecting a sensitive alarm system to these receptacles severely downgrades performance.

When did the electrical system last receive an upgrade or undergo a major modification? If you are not sure, ask yourself this question: How often are the same incandescent light bulbs replaced? If the answer is weekly, every two weeks, or even monthly, a serious problem may exist that requires immediate attention.

Is a lot of computer equipment installed throughout the building? If so, mutual interference, harmonic distortion, and neutral conductor heat buildup may occur. This type of inefficient operation can result in fires.

What kinds of electrical equipment are powered from the circuit-breaker panel serving the area where the alarm equipment will be installed? If large demand loads repeatedly turn on and off, consider selecting a different circuit-breaker panel or installing a new panel or a subpanel. If the panel directory is not marked, or worse, if it is improperly marked, the system may be connected to an incompatible power source.

What is the condition of the circuit-breaker panel that is to provide the electrical power to the console or other alarm components? If the panel is not properly maintained, problems may arise in getting the alarm system to operate correctly.

Is there enough space and electrical capacity (ampacity) for an additional breaker? Lack of physical space can be corrected by adding a subpanel. Physical space may be present, but maybe another circuit breaker cannot be added because electrical capacity will be stretched beyond safe limits.

Can an existing electrical circuit and receptacle be used, or will one or both need to be installed? Before the existing electrical circuit can be used, determine what else shares that circuit.

Ideally a dedicated circuit should be installed for the alarm console. Many manufacturers recommend that this be done, but invariably, it is not. Depending on the distance between the circuit-breaker box and the receptacle, radio frequency interference (RFI) will cause operational problems.

When RFI is severe, damage is done. Depending on the environment, a great deal of power conditioning and interference filtering may be needed.

When power conditioning is mentioned, many people think of surge protectors, although what some people refer to as surge protectors are actually spike protectors. Both surge and spike protection are important, but to be effective, they require the right equipment.

It is not enough to go to a local store and buy a power strip with metal oxide varistors and think you are completely protected. When the protection lamp goes, so does the protection.

True power conditioning must accomplish four objectives.

* Reduce all power line disturbances to levels that are harmless to an alarm system.

* Provide a clean, single point, all-purpose reference ground.

* Stop disruptive interactivity between noise generating loads.

* Provide peak current on demand without sacrificing efficiency.

Power-related problems cause disruption, degradation, and finally destruction. Disruption and degradation contribute to false alarms, while destruction takes out all or a part of the system.

Where will the console and sensors be located? Are they inside a building where temperature and humidity can be controlled? If the temperature is too high or too low, or the humidity is too high or too low, equipment will not work as designed.

Are the console and sensors exposed to the elements? If so, what precautions will be taken to ensure against the effects of rain, saltwater, and dust? Depending on the location, the equipment may have weatherized and heavy-duty air filters used.

In the place where the console or a sensor are to be located, do you know where all electrical wiring and conduits are located?

When an AC travels from one conduit back through another, and in many instances through the building's structural steel, a ground loop is created. This ground loop creates fluctuating magnetic fields that are received by the sensor or at the console, generating a false alarm.

In the location selected for a sensor or the security console, how close will it be to electrical transformers, switching gear, banks of electrical circuit breakers, or other emitters?

Voltage and phase can and do change. When electrical activity is nearby, changes created by that activity may affect the sensor's processing abilities. Currents may create electromagnetic fields so powerful that despite conditioning and filtration, the sensor is overwhelmed.

Metal can also cause interference and is found in a variety of places--metal lath is used in plaster walls and ceilings; coils of electrical or telephone wiring are found in the ceilings, under floors, and in walls; metal tracks are used for suspended ceilings and the loops of wire suspending them; decorative metal circles are used in floors, ceilings, and walls; metal handrails contain large or long loops; and metal construction studs are often used.

If the handrail is made of steel, it should be bond-grounded to structural steel. If that is not possible, the handrail should be replaced with aluminum or brass.

Metal lath, tracks, and studs that are not properly bond-grounded to structural steel, can reradiate various frequencies changing them, enriching them with harmonics, creating even more serious interference problems.

Modern sensors are immune from the effects of AM, FM, and TV broadcast frequencies. Hand-held radios, however, can cause interference in some sensors. Sensors, therefore, should not be placed within 4 feet of any public address speaker since the coils inside the speaker create electromagnetic interference.

Sensors do not operate well on a surface that is subject to vibration. Heavy truck traffic can cause this vibration. Therefore, the operation of sensors may be disrupted if they are in or near a parking garage.

One final point needs to be considered--the uninterruptible power supply (UPS). Newer computer-based alarm systems need steady power, and disruptions--regardless of duration--may generate false alarms. The UPS fills in the gaps and sags. The two kinds of UPS are standby and on-line.

The standby model reacts to a power loss by switching on. In many instances it does not switch on fast enough to preclude data loss and, thereby, generates a false alarm.

With an on-line UPS a beep or chime occurs when it fills in a sag. In some instances the action of the UPS is so subtle there is no indication of a fill in.

Nowadays, companies can no longer afford to employ large security forces to respond to spurious alarms. Alarm companies do not have the financial resources to maintain a staff of specialists and installers to check and recheck systems constantly.

And when security forces spend the majority of their time in a reactive mode, little time is left for taking a preventive role. However, site preparation, correct sensor selection, smart installation techniques, power conditioning, and UPS--if required--can eliminate the gremlins.

William J. Warnock is president of Warnock Security Solutions Inc. in Haymarket, VA. He is a member of ASIS.
COPYRIGHT 1992 American Society for Industrial Security
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Author:Warnock, William J.
Publication:Security Management
Date:Sep 1, 1992
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