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  • Low Frequency Emergency Signaling Handbook

    A practical guide to compliance and its history

  • Low Frequency Emergency Signaling Handbook

    A practical guide to compliance and its history

    2015 United Technologies Corporation

    All rights reserved. Specifications are subject to change without notice.

    EDWARDS is part of UTC Building & Industrial Systems.

    1016 Corporate Park Drive, Mebane, NC 27302

    85000-0394

    This handbook is for information only, does not provide legal or compliance advice and is not

    intended as a substitute for verbatim legislated requirements. For authoritative

    specifications regarding the application of life safety and incident management systems,

    consult current editions of applicable codes and standards. For authoritative interpretation

    of those codes and standards, consult your local authority having jurisdiction.

    While every effort has been made to ensure the accuracy and completeness of this

    handbook, the authors and publishers assume no responsibility for errors, inaccuracies,

    omissions, or any inconsistencies herein.

    EDWARDS and Genesis Series are trademarks of United Technologies Corporation.

    Low Frequency

  • Emergency Signaling Handbook

    A practical guide to compliance and its history

    Contents Introduction .................................................................................................................................................. 1

    Compliance only part of the picture ......................................................................................................... 1

    Background: History of Horns ....................................................................................................................... 3

    Waveforms: The Ups and Downs of Sound .................................................................................................. 5

    The 520 Hz Wave ...................................................................................................................................... 6

    Wakeup Calls: Codes and Mandates ............................................................................................................. 8

    Audible devices ........................................................................................................................................... 10

    Horns ....................................................................................................................................................... 11

    Horn-strobes ........................................................................................................................................... 12

    Sounder Bases ......................................................................................................................................... 14

    Audio devices .............................................................................................................................................. 14

    End-to-end-compliance .......................................................................................................................... 14

    Speakers and speaker-strobes ................................................................................................................ 15

    Compatibility Lists: Check Them Twice ....................................................................................................... 18

    Application Checklist ................................................................................................................................... 19

    Retrofits: When and Where ........................................................................................................................ 21

    Non-sleeping Areas: Is 520 Hz necessary? .................................................................................................. 22

    Better Life Safety: Making the Right Calls ................................................................................................... 23

  • Low Frequency Signaling Handbook | Introduction 1

    Introduction

    In 2010, NFPA 72 the National Fire Alarm and Signaling Code was amended to generally require low

    frequency 520 Hz warning tones in newly constructed commercial sleeping areas where audible

    appliances are provided. The change went into effect on January 1, 2014. Many jurisdictions across the

    U.S. have adopted the 2010 and 2013 NFPA 72, either directly or through codes such as the

    International Fire Code and the International Building Code. However, as noted in the National Fire

    Protection Association (NFPA) January/February 2015 blog, many U.S. contractors were surprised by the

    requirements compliance date1. Additionally, the proposed 2016 version of NFPA 72 includes revisions

    that will provide more specifications on testing and listing appliances that produce the low-frequency

    tone2.

    The implementation of changing to low frequency signals isnt as complex for commercial fire systems

    as previous revisions. For example, the adoption of synchronized strobes required modifications to

    circuitry that precipitated external modules and to timed synchronizing pulses to eliminate random

    flashes of light in the same line of sight. By comparison, devices and functionality for low frequency

    signaling are already in place for many commercial systems. Also, since the provisions only apply to new

    construction or significant renovations, there is no need to retrofit existing installations.

    Some life safety systems may need special design consideration to accommodate low frequency

    notification. Power supplies, amplifiers, audio source units, horns, sounders, and speakers all play a part

    in achieving code-compliant 520 Hz signaling. The ease or difficulty with which the new requirements

    are deployed depends on the system and the manufacturer. Even if its as simple as specifying different

    horns or speakers for sleeping areas, there remains the challenge among life safety designers and

    building owners of using these signals with the greatest life-saving effect and in compliance with local,

    state, and national codes.

    Compliance only part of the picture

    Like all life safety changes, low frequency signaling has raised its share of questions about compliance

    and application, best practice, commercial viability, customer considerations and even compatibility.

    These concerns make an uncomplicated and straightforward implementation an elusive objective.

    Compliance with codes and standards is only part of the picture. As minimum requirements, they dont

    take into account the nuances of good system design. Even the local authority having jurisdiction (AHJ)

    may be concerned with whats right for a particular setting from a compliance point of view.

    1 NFPA.org, http://www.nfpa.org/newsandpublications/nfpa-journal/2015/january-february-2015/in-

    compliance/nfpa-72

    2 http://www.nfpa.org/newsandpublications/nfpa-journal/2015/may-june-2015/features/nfpa-72

  • Low Frequency Signaling Handbook | Introduction 2

    The primary objective of a life safety system is to keep building occupants safe to the extent feasible.

    The trick for a system designer is distinguishing what can be done from what should be done; separating

    what is possible from what is practical. Optimal solutions arise where training and experience meet

    good information. Even with life safety there are trade-offs between cost and effectiveness, and the cost

    doesnt have to be monetary. For example, cranking up the effective decibel (dB) of a horn will

    eventually awaken even the soundest sleeper, but it could also result in hearing loss, ruptured eardrums

    or even organ damage. Similarly, system effectiveness needs to be balanced with system overhead. A

    good designer will know how to prevent a good plan from becoming cost prohibitive.

    Understanding this issue means understanding the reasoning behind it and the circumstances that lead

    to its adoption. Only then can decisions be made that act in the best interests of building owners,

    designers, and occupants.

  • Low Frequency Signaling Handbook | Background: History of Horns 3

    Background: History of Horns

    The road to low frequency signals begins approximately 40 years ago, after the transition from using

    electro-mechanical buzzers and mechanical bells to electronic horns. This innovation simplified fire

    alarm system signaling and increased the number of signals a typical system could handle.

    These new devices produced audible output at a much higher auditory frequency than their

    predecessors: about 3,000 Hz. Evidence soon emerged that this pitch may not be as effective at waking

    the hearing impaired. According to a National Center for Health Statistics report, 37.5 million Americans

    suffer from some hearing loss.3 Fueled by the Americans with Disabilities Act (ADA), and mandated by

    the widespread adoption of UL 1971 (Signaling Devices for the Hearing Impaired), the fire alarm strobe

    became the primary ADA compliant signaling throughout the 1990s, and remains the de facto standard.

    The next evolution came following a series of studies testing the various ways of awakening at-risk

    populations, including children, older adults and hearing impaired. Conducted by Dorothy Bruck and Ian

    Thomas at the Centre for Environ

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