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Wireless wonders.


COMMERCIAL BUILDINGS ARE LIKE TECHNOLOGY--the only constant is change. Changes in technology raise expectations, and raised expectations result in the demand for better ways of doing things. For buildings, changes mean they will require expansion, upgrading, renovation, or retrofitting of their systems. This need may result from a change in building or fire codes, building use, or tenant or client needs or from a desire for an increased level of sophistication arising from threat assessment or potential liability exposure.

The challenge for the security professional is to keep pace with security, fire and life safety, and asset protection technology. Because of code revisions, obsolescence, or the inherent limitations of existing systems, a new system is often the best--if not the only--solution. Although security managers traditionally concentrate on operations, they should participate in selecting, specifying, and supervising security and safety systems that complement staffing and other operational facets of the job.

One result of these constant demands for innovations is commercial wireless technology. A new twist on an old idea, the technology is used in residential, individual business, and personal medical emergeny applications. Advancements in the technology have afforded other opportunities, such as additional Underwriters Laboratories (UL) listings and National Fire Protection Association (NFPA) compliance for life/safety applications.

Wireless systems consist of a device such as a smoke detector that transmits a signal; a repeater that receives, validates, and then rebroadcasts the signal; and a control panel that receives and prioritizes the signal and acts on it. Each device transmits an alarm via a low-power, digitally coded radio signal, and the control panel annunciates it. The panel is also capable of operating ancillary devices such as an automatic dialer or initiating relays to facilitate elevator recall.

A wireless system functions through a repeater network that is similar to the cellular networks used by mobile telephones. In a given application--a building, group of buildings, parking lot, or campus--repeaters are strategically placed to ensure that all device signals can be received and rebroadcast successfully to the receiving control panel. A redundant or overlapping network design ensures system integrity.

Innovations in transmission format (how the signal is sent) and receiver technology (the ability to receive the signal) have allowed for the development of systems that effectively meet the stringent testing necessary for use in commercial applications. The information sent by devices in early applications was formatted in Manchester coding, in which the data sent is broken down into a series of long and short signals. Interference often caused the signals to be lost or altered, resulting in the receipt of inaccurate information and therefore missed or false alarms.

Today signals are sent through tone-encoded modulation in which the data is broken down into a burst of unique tones that are impervious to distortion or alteration. The use of these signals has effectively negated missed transmissions.

Also, receiver types were changed from superregenerative to superheterodyne, which monitors a smaller frequency range and thus limits extraneous noise received (a higher signal-to-noise ratio means better reception). Receivers are now microprocessor controlled so they can lock onto and track signals. In addition, the microprocessor allows for the receipt and processing of several simultaneous signals.

Systems employing this combination were given strenuous throughput tests (no more than one missed signal per million) by UL (listing standard #1730 and throughput tests #985 and #1023) and have subsequently been approved and listed for use in commercial fire annunciation and detection applications. In addition, this type of system was the model for the revision of NFPA's 72A amendment allowing use of low-power wireless in commercial protective signaling systems. This change represents a substantial achievement after 90 years of only hard-wired specifications.

COMMERCIAL WIRELESS OFFERS numerous advantages over traditional hard-wired systems. Wireless systems offer more exact information in that each device is individually addressed so a problem is immediately pinpointed. Wired systems would require point-to-point wiring to offer the same capability, and, in the interest of economics, the typical wired system is broken down into zones instead of individual devices.

Wireless systems offer constant supervision (each device and repeater sends continuous signals that the control panel monitors and tracks) to ensure system integrity. They not only annunciate alarm and trouble conditions but also indicate low battery conditions, tampering, and frequency jamming. The failure of an individual device does not compromise other devices in a wireless system.

Wireless systems are flexible and allow for expansion. Supplemental addons for personal and property protection or personal emergency are easily accomplished within the same system. Any device that can be monitored, controlled, or activated through a set of electrical contacts is compatible with a wireless system. This includes smoke detectors, pull stations, flow and tamper switches, motion and intrusion detectors, and glass breakage and door contact devices.

Individually identified by type, location, and alarm condition, these devices are all monitored from the same control panel. Portability is a strong advantage in that if an office is renovated or remodeled, any device can be relocated without rewiring.

Mobile applications are also currently in use in correctional and court-house facilities. Law enforcement officers, judges, and other courtroom personnel carry pager-sized devices equipped with panic buttons that immediately notify emergency response personnel of the problem, location, and individuals involved.

Commercial wireless also alleviates installation headaches because, as the name implies, there is no wiring. Installation is substantially faster than with wired systems, thus reducing business disruption and downtime. It is also cleaner: No core-boring or any of the other messy necessities associated with wiring are required. Older, plaster-walled buildings require no wire mold, and aesthetics are preserved, an important feature if historic preservation is involved. The speed and ease of installation can result in an average savings of 25 to 40 percent, based on reduced labor and materials alone.

The attractiveness of commercial wireless technology is that systems using it are designed to grow as the technology does, not be rendered obsolete by it. The need to start over again is all but eliminated. Research and development in possible applications make commercial wireless a good alternative not only for today but for the future as well.

About the Authors ... Chris King and John Dickson are licensed security consultants with WJA Security Services Company, which is based in Dallas, TX. The company serves the commercial high-rise and lodging industries and specializes in system design applications of this technology. Both authors are members of ASIS.
COPYRIGHT 1989 American Society for Industrial Security
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Title Annotation:wireless alarm systems
Author:King, Chris; Dickson, John
Publication:Security Management
Date:Apr 1, 1989
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