Low Frequency Emergency Signaling Handbook - Edwards Safety Hz Signaling Handbook… · Low Frequency Signaling Handbook | Introduction 2 The primary objective of a life safety system

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.

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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


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

requirement’s 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 isn’t 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 it’s 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 don’t

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

may be concerned with what’s 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

doesn’t 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 Environmental Safety and Risk Engineering at Victoria University in Melbourne,

Australia, the research projects compared the effectiveness of notification appliances ranging from

recorded messages to strobes to bed shakers to horns of different auditory and temporal frequencies,

including the standard 3,000 Hz pure tone, as well as a 400 Hz and 520 Hz square wave tones.4 In each

case, researchers measured the length of time needed to awaken test subjects.

Why focus so much on sleep? Because studies show that is when people are most vulnerable to the

danger of fire. The U.S. Fire Administration reports 46 percent of fatal residential fires start between 10

p.m. and 6 a.m., and fatal incidents peak between 3 a.m. and 4 a.m., when most people are in deep

sleep.5

Their initial findings prompted the NFPA’s research wing, The Fire Protection Research Foundation, to

commission further study. Funded by the U.S. Fire Administration, the final report was published in 2007

and culminated nearly ten years of work.6 The results found that a 520 Hz square wave tone may be

more effective at awakening the hearing impaired, older adults and adults who had elevated blood-

alcohol levels or who were sleep-deprived. It also was the second most effective way to wake young

children – following a voice warning.

3Blackwell DL, Lucas JW, Clarke TC. Summary health statistics for U.S. adults: National Health Interview

Survey, 2012. National Center for Health Statistics. Vital Health Stat 10(260). 2014, p. 40.

4Thomas, Ian and Bruck, Dorothy (2008) Awakening of Sleeping People: A Decade of Research.

5 U.S. Fire Administration (2008), “Residential Structure and Building Fires,” p. 20.

6Bruck, Dorothy; Ian, Thomas (June 2007), "Optimizing Fire Alarm Notification for High Risk Groups)",

Fire Protection Research Foundation, Research Project.

http://www.cdc.gov/nchs/data/series/sr_10/sr10_260.pdf

http://www.cdc.gov/nchs/data/series/sr_10/sr10_260.pdf

https://en.wikipedia.org/w/index.php?title=Fire_Protection_Research_Foundation&action=edit&redlink=1

Low Frequency Signaling Handbook | Background: History of Horns 4

Based on these findings, the Fire Protection Research Foundation study stated categorically that “any

recommendations for the use of strobe lights, presented alone, as an emergency alarm to awaken

sleepers who are hard of hearing or of normal hearing should be withdrawn as soon as possible.”

Instead, it clarified that that strobes continue to have value for people who are awake, particularly in

areas of high ambient noise, and as an emergency alert for people who are deaf.7 The NFPA 72 code was

also amended to require 520 Hz signaling in newly constructed and some renovated commercial

sleeping areas that contain fire alarm systems.

The research findings also demonstrated that voice messaging intelligibility is an important factor, even

when asleep. The study found that non-English speakers did not awaken as readily as English speakers

when presented with high dB voice audio in English. This result debunks the theory that, a message may

still be carried with sufficient sound pressure to awaken an individual regardless of whether they

understand the warning. It seems instead, that words and meaning do break through even a deep

sleep.

7Bruck, Dorothy; Ian, Thomas (June 2007), Optimizing Fire Alarm Notification for High Risk Groups, Fire

Protection Research Foundation, Research Project, p. 11.

Low Frequency Signaling Handbook | Waveforms: The Ups and Downs of Sound 5

Waveforms: The Ups and Downs of Sound

Sounds of particular frequencies travel differently than others. Robert Foulis, the inventor of the fog

horn, struck upon the idea for his new long-range warning apparatus when he heard his daughter

playing the piano from a distance. He could only hear some of the notes — the lower frequency ones.

Similarly, the common dog whistle shows that not all hearing is the same. The dog whistle emits a tone

at a frequency that is above the threshold of human hearing — but which canines can hear.

The way an individual perceives sound depends on physiological factors such as the condition of the ear

and its components including the eardrum, the cochlea, and the tiny hairs that convert sound energy to

electrical signals. The individual’s age, an injury, atmospheric conditions, or congenital impairment all

can have an effect. Neurological factors also affect how the brain processes electrical impulses

generated by the inner ear. An individual’s sleep state, drug use, alcohol impairment, and even their

mental state can impact how sound is perceived, or if it is heard at all.

The combinations of factors that can cause people to hear the same sound differently are virtually

limitless, and, along with energy considerations, facility layout, cost considerations and other factors,

creates a challenge for an alarm system to reach and be understood by as many people as possible.

Making a signal louder eliminates some of the disparity, but there are practical and physical limits to

how loud a signal can and should be, as well as practical and commercial limits on the types of devices

available and potential combination of technologies. There are also more subtle ways to improve

audibility in exchange for less energy.


The 520 Hz Wave

Sound takes the form of waves that travel through the atmosphere from their source. Auditory

frequency represents the distance in time between two of these waves. It is related to what we perceive

as pitch. The height of the waves, referred to as amplitude, is related to what we perceive as sound

pressure, or loudness. Sound level is to auditory frequency what voltage is to current, or volume is to

pressure.

Sound frequency is expressed as Hertz (Hz), a unit of measure that represents one wave per second. A

tone of 1 Hz isn’t really a tone because the frequency needs to be much higher to register as a

perceptible note. The standard fire alarm signal, which does have some advantages, is generated at a

3,000 Hz frequency with a sound level output at 75 to 90 dB (decibels).

A 520 Hz tone is a waveform that repeats 520 times per second. Its discovery as a potential tonal sweet

spot came when researchers began to look not only at the sound wave’s frequency but at the shape as

well.

Waveform shapes are split into four broad categories

that describe its path from one occurrence to the next.

The shape affects how the tone sounds. The sine wave

is most commonly regarded as a typical wave; it

describes a sweeping line from the peak of one wave to

the peak of the next in a smooth symmetrical arc. The

standard 3,000 Hz alarm signal employs a sine wave

referred to as a pure tone.

The square wave describes a wave with right angles and

straight lines across the horizontal and vertical axis only.

It resembles a castle rampart. Other waveform shapes

include triangle and sawtooth.

Changing a tone’s waveform shape changes the

character of its sound without altering its pitch. Listen to

the differences below:

Frequency, waveform Sample8

3,000 Hz Sine Wave (Pure Tone) 3000.wav

8 Files are for demonstration purposes only. Not for use as life safety signals.

Figure 1 The shape of sound waves determine their pitch and sound characteristics.


520 Hz Sine Wave (Pure Tone) 520 Sine.wav

520 Hz Square Wave 520 Square.wav

The 520 Hz square wave isn’t really square; it has blips and bounces, known as harmonics. In order for

the tone to meet their standards, listings agencies such as Underwriters Laboratories (UL) require that

these harmonics appear at prescribed frequencies and reach predetermined amplitudes relative to each

other and relative to the primary 520 Hz band.

Figure 2 Tones that meet UL requirements include a primary waveform at the 520 Hz mark (seen at the left of this chart), as well as a series of harmonics at predetermined frequencies.

The chart above shows the primary 520 Hz band at the left followed by three harmonics. In order for a

life safety system to pass UL’s low frequency testing, it must faithfully reproduce the benchmark tone

and its output must exhibit the same acoustic properties, including harmonics.

Low Frequency Signaling Handbook | Wakeup Calls: Codes and Mandates 8

Wakeup Calls: Codes and Mandates

The study concluded that the 520 Hz square wave tone was the best overall tone for awakening sleeping

individuals, especially those with hearing impairment. The Fire Protection Research Foundation also

recommended to “replace the current high frequency smoke alarm T3 signal with a low frequency

square wave T3 signal”9.

This research kicked off a series of NFPA technical committee meetings and reports that resulted in

changes to the 2010 Edition of NFPA 72: National Fire Code. The revisions require 520 Hz signals in

newly constructed commercial sleeping areas such as dormitory rooms, hotel rooms, sleeping rooms in

retirement and assisted living facilities where audible appliances are provided, and in some jurisdictions,

bedrooms in multi-unit residential buildings such as apartments and condominiums. The NFPA did not

require modification of the signals for residential smoke alarms.

In NFPA 72, chapters 18, 24, and 29 of the code were affected:

NFPA 72, Chapter 18 requires the installation of low frequency audible fire alarm signals in all

applicable sleeping areas to provide the widest possible

benefit. Surveys show many hearing impaired adults

don’t identify themselves as such often because they are

not aware of the impairment, or do not believe it is

severe enough to warrant special accommodation. Also,

the studies allege that the 520 Hz signaling benefits

children, older adults, and those impaired by alcohol or

medication. NFPA 72, Chapter 24 requires the

integration of a 520 Hz signal into the messaging

platform for voice audio and mass notification systems.

It calls for two cycles of a Temporal 3 (T3) 520 Hz tone to

be broadcast to sleeping areas at the beginning of every voice message. This revision aligns with

established requirements found in NFPA 72 and UL 864.

Excluded from the provisions of NFPA 72 Chapter 18

and Chapter 24 are healthcare facilities,

correctional/detention facilities and other occupancies

where private mode signaling is employed and where

staff are trained to alert and evacuate occupants

according to established protocols.

NFPA 72, Chapter 29 requires 520 Hz signals in all sleeping areas where standalone smoke

alarms or household fire alarm systems are installed and used to awaken people with mild to

9 Bruck, Dorothy; Ian, Thomas (June 2007), Optimizing Fire Alarm Notification for High Risk Groups, Fire Protection

Research Foundation, Research Project, p. 10.

18.4.5.3 Effective January 1, 2014, where

audible appliances are provided to produce

signals for sleeping areas, they shall

produce a low frequency alarm signal that

complies with the following:

(1) The alarm signal shall be a square

wave or provide equivalent awakening

ability.

(2) The wave shall have a fundamental

frequency of 520 Hz ± 10 percent.

24.4.2.4.3 In areas where sleeping

accommodation are provided, but the voice

communication system is used to

communicate to occupants who are awake,

the low-frequency tone shall not be

required.

Low Frequency Signaling Handbook | Wakeup Calls: Codes and Mandates 9

severe hearing loss. This provision differs from Chapters 18 and 24 as those refer to protected

premises systems typically installed in commercial facilities and multi-unit residential buildings.

Chapter 29 refers to residential fire alarm systems or standalone devices that cover a single

household or portion. What this means is that households subject to NFPA 72 only require 520

Hz signals if it will be used to awaken someone known to have hearing loss. This is consistent

with rules governing notification systems for people with disabilities, i.e.: the Accessibility

Guidelines under the Americans with Disabilities Act (ADA).

The NFPA 72 provisions apply to new commercial construction only and certain renovations. Single

family residences are not affected. The compliance deadline was January 1, 2014.

The 2015 Edition of NFPA 720: Standard for the Installation of Carbon Monoxide (CO) Detection and

Warning Equipment was also updated to include low frequency signaling. This code applies to the

installation of carbon monoxide detectors, which are required to initiate audible signals that can be

differentiated from those of smoke and heat detectors.

In NFPA 720, Chapter 6 was affected:

NFPA 720, Chapter 6 requires 520 Hz signals in sleeping

areas. Carbon monoxide events are typically signaled by

T4 tones, which are repeating patterns of four tones

followed by a pause. Fire alarm events are signaled by

T3 patterns, which are three tones followed by a pause.

NFPA 720 requires that those T4 signals be 520 Hz

square wave tones in sleeping areas.

Like NFPA 72, the 520 Hz provisions of NFPA 720 apply to new

commercial construction only. The compliance deadline was

January 1, 2015.

6.4.4.3 Effective January 1, 2015, where

audible appliances are provided to produce

signals for sleeping areas, they shall

produce a low frequency alarm signal that

complies with the following:

(1) The alarm signal shall be a square

wave or provide equivalent awakening

ability.

(2) The wave shall have a fundamental

frequency of 520 Hz ± 10 percent.

Low Frequency Signaling Handbook | Audible devices 10

The 520 Hz Solution

Audible devices

For systems that do not include voice audio, designing a new 520 Hz application is a matter of selecting

horns that meet UL 464 (Audible Signaling Appliances) low frequency requirements. The control system

also needs to be listed as one that will support 520 Hz signaling.

Notification appliances that meet UL 464

are labeled on the device’s nameplate.

These appliances are listed and approved

for sleeping areas that require the 520 Hz

tone in accordance with NFPA 72.

Edwards brand UL 464 listed audible

devices include horns and horn-strobes, as

well as sounder bases for smoke and CO

detectors. For sleeping rooms, most codes

and standards require a sound pressure

level of at least 75 dB- at the pillow.

Figure 3 Nameplate labels found on notification appliances that have been UL listed for 520 Hz signaling in sleeping areas state that the device is for low frequency applications, and show the UL listed mark.


Horns

The Edwards 520 Hz horn solution is provided by the G4LF Series of notification

appliances. These low-profile devices offer the benefits of Genesis Series life

safety signals with output suitable for sleeping areas requiring UL 464 listed

low frequency tones.

G4LF horns generate the 520 Hz tone in the standard T3 temporal pattern. An

optional setting configures the appliance for continuous audible output, which

is a critical feature for notification appliance circuits controlled by a coder

module such as the CDR-3.

When connected to compatible Edwards control equipment, G4LF Series

audible 520 Hz output remains synchronized with all Genesis Series audible

signals on the same notification appliance circuit. 520 Hz and standard 3,000

Hz Genesis audible signals can be mixed on the same circuit and still

synchronize together per NFPA 72.

These devices are also field-configurable for high or low dB output; a jumper cut will reduce the audible

output by about five dB. This allows each device to be tuned to the specific sound requirements of the

room in which it is installed, increasing opportunities to reduce system overhead and installation costs.

Horn-only models may be ceiling- or wall-mounted, providing more positioning options for delivering

the required dB output level.

Figure 4 Low frequency horns are clearly marked 520 Hz on the front of the device. This is to distinguish it at a glance from standard horns.


Horn-strobes

Combination horn-strobes deliver UL listed 520 Hz alarms with a strobe signal.

The single housing requires only one wall opening and electrical box.

In addition to meeting UL 464, these devices also must meet UL 1971

(Signaling Devices for the Hearing Impaired) requirements, which include light

output intensity levels and limiting flashes within the same field of view in

order to avoid the risk of seizures for people with photosensitive epilepsy

(PSE).

The UL 464 and UL 1971 performance standards must be met in accordance

with NFPA 72, which sets audible and visible requirements for specific

applications such as sleeping areas.

When installed with a signal master module or other compatible control

source, Genesis Series horn-strobes allow independent horn control over a

single pair of wires. Two control methods are available: traditional NAC signal silence or normally-closed

contact. Both may be used to silence horns without turning off strobes on the same circuit. This value-

added feature saves the expense of running separate wires where independent horn control is required.

Commercial sleeping areas covered by NFPA 72 require a strobe light within 16 feet of the pillow. If the

device is wall-mounted and located 24 inches or further from the ceiling, it should have a light output

intensity of 110 cd or greater. If the strobe light is ceiling or wall-mounted closer than 24 inches to the

ceiling, it must be 177 cd or greater. It also must provide 75 dB sound pressure level at the pillow.

Figure 6 Where horn-strobes are used in sleeping areas, the device must meet UL 1971 placement criteria for strobe lights, as well as minimum sound levels at the pillow for the device's audible function.

The placement of a combination horn-strobe in a sleeping area can be a challenge. Thankfully, Edwards

has many options available. G4LF horn-strobes may be field configured for high or standard 520 Hz

audible output (dB) and there are four different light intensity settings. Housings come in either red or

white, and with or without FIRE markings.

Figure 5 Horn-strobes must meet the UL 464 standard for audible devices, as well as UL 1971 standards for visible signals.


Combined, these options offer a range of solutions that meet most audible and visible sleeping room

requirements for emergency signals. The following 520 Hz horns and horn-strobes are available from

your Edwards equipment supplier. Consult the data sheet for product details and specifications.

Horns and Horn-strobes, Data Sheet 85001-0639

Model Housing

Color Text

Marking Horn Output

Strobe Output

G4LFWN-HVM White

None

Low Frequency

(520 Hz)

with

selectable

High/Low

dB output

Selectable

15, 30, 75, or 110 cd

G4LFWF-HVM FIRE

G4LFRN-HVM Red

None

G4LFRF-HVM FIRE

G4LFWN-H White

None

Horn-only models G4LFWF-H FIRE

G4LFRN-H Red

None

G4LFRF-H FIRE

Low Frequency Signaling Handbook | Audio devices 14

Sounder Bases

Edwards 520 Hz sounder bases add UL 464 listed low

frequency audible tones to the entire Edwards line of

intelligent smoke, heat, and CO detectors. When

mounted with a matching detector, these bases provide

an unobtrusive alternative to separately installed horns

and detectors. The combination also reduces cost by

only using one electrical box and one wiring run.

Like wall horns, these sounder bases produce a

distinctive 520 Hz signal. Audible signals may be

configured for either coded or non-coded signal circuits.

Sounder bases are subject to the same dB output

requirements for sleeping areas as wall and ceiling

mounted horns — 75 dB at the pillow. They are audible

devices only and do not have a visible, i.e. strobe, component.

Sounder bases on the same circuit may be activated as a group or zone, which sometimes requires the

use of a polarity reversal module. The group or zone may be set for synchronized audible output with

the use of a signal master module or other compatible control source.

Some sounder bases are compatible with carbon monoxide (CO) detectors. NFPA 720 (Standard for the

Installation of Carbon Monoxide Detection and Warning Equipment) requires a distinctive temporal

pattern to warn of CO in order to differentiate it from fire. CO events are signaled by a T4 pattern,

which consists of four beeps followed by a pause. Smoke alarm events are signaled by a T3 pattern,

which consists of three beeps followed by a pause.

Sounder bases that support both CO and fire detection require a temporal pattern generator installed

on the same data loop to synchronize the T3 and T4 patterns. Fire/CO sounder bases have two operating

modes: fire output only, which emits the T3 pattern and Fire-plus-CO, which emits both patterns. .

Audio devices

End-to-end-compliance

The distinction between audio and audible devices represents a wide gulf in function. Audible devices

refer to horns. They produce the 520 Hz tone by virtue of their electronic properties, i.e.: if the

operating voltage is applied to the device, then the sound is produced. Audio devices are part of a larger

system that includes amplifiers, microphones, and source units that produce sound from audio signals.

They are used in voice evacuation systems to play live or recorded messages. (Voice evacuation systems

are usually required in buildings more than six levels or 75 feet high; refer to local codes for specifics.)

Figure 7 Sounder bases provide a clean, integrated look and reduce installation costs by requiring only one electrical box and wiring run for both the detector and the sounder.


Where voice evacuation systems are present, NFPA 72 requires that the system produce a preannounce

tone immediately prior to the live or recorded message. Since this tone must be a 520 Hz square wave

generated by a UL 464 listed audio evacuation system in sleeping areas, a system needs end-to-end

compliance.

End-to-end compliance requires that all relevant audio components contributing to the production of

the warning signal be tested and certified to ensure that the UL-defined 520 Hz square wave tone is

produced accurately and consistently. That includes the control system, audio source unit, amplifier,

speaker, and even the 520 Hz .wav file. Once evaluated together as a working system under controlled

conditions, it is then approved and listed to UL 864 and UL 464.

Any audio system may be able to play a 520 Hz .wav audio file, and it may sound to the untrained ear

just like any other 520 Hz square wave tone. But for listing purposes, if it isn’t UL approved, it does not

comply with NFPA low frequency emergency signaling requirements.

For new installations that include sleeping areas, the system designer needs to ensure end-to-end

compliance. Refer to the current system compatibility list, which specifies the arrangement of hardware

components and software necessary to qualify. Some manufacturers may require special amplifiers and

control equipment to gain the UL 464 listing.

Edwards audio systems have achieved, without any modification or upgrade, UL 464 listings for all

currently supported amplifiers and control equipment. These components may be specified without

special consideration for 520 Hz sleeping areas. Only the speakers installed in sleeping areas need to be

specially selected.

Speakers and speaker-strobes

Edwards has a wide variety of 520 Hz ready speakers and speaker-strobes

available. These include wall and ceiling models, as well as speaker-only units

and combination speaker-strobes.

Optional amber lens tints, ALERT or FIRE markings, and red or white housings

ensure there is a 520 Hz-ready speaker for every application, including mass

notification.

Edwards speakers feature selectable wattage taps, while speaker-strobes

allow for both wattage and light output levels to be configured in the field.

This makes it easier to order, stock, stage, track and inventory because the

same unit can be used for a range of room sizes and layouts.

Wattage tap and light output settings remain clearly visible, even after final installation, allowing devices

to be fine-tuned to achieve its maximum benefit in exchange for the lowest possible system overhead.

Models for both 25 and 70 VRMS audio circuits are available.

Figure 8 Versatile speakers and speaker-strobes may be used for fire alarm, CO alarm, and mass notification purposes.


Edwards 520 Hz ready speakers derive the added benefit of high fidelity performance from their ability

to produce the UL-approved low frequency tone. This means they produce crisper, clearer voice audio

output that is highly intelligible over large areas. These speakers also offer potential cost benefits. For

example, when used in non-sleeping areas, it may be possible to place fewer Edwards high fidelity

speakers over the same area compared to standard speakers and still achieve the same audibility.

The following 520 Hz High Fidelity speakers are available and part of a UL listed end-to-end audio system

solution. Consult the data sheet for product details and specifications, and consult the appropriate

system compatibility list for application suitability.

Wall Speakers and Speaker-Strobes, see Data Sheet 85001-0642.

Model Housing

Color Text

Marking Lens Color

Strobe Output

Speaker Voltage

Life Safety 520 Hz High Fidelity Appliances

G4HFWN-S2 White None

Speaker only models

25 Volt

(Selectable ¼, ½, 1, or 2 watt)

G4HFRN-S2 Red

G4HFWF-S2 White FIRE

G4HFRF-S2 Red

G4HFWN-S2VMC White None

Clear Selectable

15, 30, 75, or 110 cd

G4HFRN-S2VMC Red

G4HFWF-S2VMC White FIRE

G4HFRF-S2VMC Red

G4HFWN-S7 White None

None Speaker only models

70 Volt


G4HFRN-S7 Red

G4HFWF-S7 White FIRE

G4HFRF-S7 Red

G4HFWN-S7VMC White None

Clear Selectable

15, 30, 75, or 110 cd

G4HFRN-S7VMC Red

G4HFWF-S7VMC White FIRE

G4HFRF-S7VMC Red

Mass Notification 520 Hz High Fidelity Appliances

G4HFWA-S2VMA

White

ALERT Amber Selectable 13, 26, 65, or 95 cd

25 Volt


G4HFWA-S2VMC Clear Selectable 15, 30, 75, or 110 cd

G4HFWN-S2VMA None Amber Selectable 13, 26, 65, or 95 cd

G4HFWA-S2 ALERT Speaker Only Model

G4HFWA-S7VMA

White


70 Volt


G4HFWA-S7VMC Clear Selectable 15, 30, 75, or 110 cd

G4HFWN-S7VMA None Amber Selectable 13, 26, 65, or 95 cd

G4HFWA-S7 ALERT Speaker Only Model


Ceiling Speakers and Speaker-strobes, see Data Sheet 85001-0641.

Model Housing

Color Text

Marking Lens Color

Strobe Output

Speaker Voltage

Life Safety 520 Hz High Fidelity Appliances

GCHFRF-S2VMC Red FIRE

Clear Selectable

15, 30, 75, or 110 cd

25 Volt


GCHFWF-S2VMC White

GCHFRN-S2VMC Red None

GCHFWN-S2VMC White

GCHFRF-S2VMCH Red FIRE

Clear Selectable

95, 115, 150, or 177 cd

GCHFWF-S2VMCH White

GCHFRN-S2VMCH Red None

GCHFWN-S2VMCH White

GCHFRF-S2 Red FIRE

Speaker only models GCHFWF-S2 White

GCHFRN-S2 Red None

GCHFWN-S2 White

GCHFRF-S7VMC Red FIRE

Clear Selectable

15, 30, 75, or 110 cd

70 Volt


GCHFWF-S7VMC White

GCHFRN-S7VMC Red None

GCHFWN-S7VMC White

GCHFRF-S7VMCH Red FIRE

Clear Selectable

95, 115, 150, or 177 cd

GCHFWF-S7VMCH White

GCHFRN-S7VMCH Red None

GCHFWN-S7VMCH White

GCHFRF-S7 Red FIRE

Speaker only models GCHFWF-S7 White

GCHFRN-S7 Red None

GCHFWN-S7 White

Mass Notification 520 Hz High Fidelity Appliances

GCHFWA-S2VMA

White


25 Volt

(Selectable ¼, ½, 1, or 2

watt)

GCHFWN-S2VMA None Amber

GCHFWA-S2VMC ALERT

Clear Selectable 15, 30, 75, or 95 cd

GCHFWA-S2VMAH Amber Selectable 82, 100, 130, or 155 cd

GCHFWN-S2VMAH None Amber

GCHFWA-S2VMCH ALERT


GCHFWA-S2 Speaker only model

GCHFWA-S7VMA

White


70 Volt

(Selectable ¼, ½, 1, or 2

watt)

GCHFWN-S7VMA None Amber

GCHFWA-S7VMC ALERT


GCHFWA-S7VMAH Amber Selectable 82, 100, 130, or 155 cd

GCHFWN-S7VMAH None Amber

GCHFWA-S7VMCH ALERT

Clear Selectable 95, 115, 150, 177

GCHFWA-S7 Speaker only model

Low Frequency Signaling Handbook | Compatibility Lists: Check Them Twice 18

520 Hz Application

Compatibility Lists: Check Them Twice

System design for UL 464 listed low frequency signaling in required sleeping areas begins with the right

equipment. A horn is a simple on-off device with a fixed audible output at operating current. The

nameplate label on the device will state that it is UL listed for 520 Hz signaling applications. When placed

in a bedroom and generating at least 75 dB at the pillow, these devices will meet the basic requirements

under UL 1971 for sleeping areas.

Audio voice systems are more complex. Even though a system may be capable of playing a 520 Hz

square wave pre-announce .wav file, it may not generate a true representation of the tone as defined by

UL. Off-spec harmonics, acoustic interference, audio distortion, and amplifier or speaker limits can cause

an impact. Only listed equipment will demonstrate to the local AHJ that the installation meets UL 464 in

accordance with referenced building codes.

There is no consistent means of labeling the equipment. Horns and speakers will have a label on the

back. Sometimes there is also 520 Hz indication on the front. Amplifiers and other equipment may or

may not be labelled as being UL 464 Listed explicitly for 520 Hz signaling.

To ensure the entire audio system supports 520 Hz signaling, life safety designers need to closely

consult the compatibility list issued by the manufacturer for the control system that will manage the

audio. This list will document all equipment, including amplifiers, speakers, and the sound file that

have been approved and listed. Be sure to obtain the latest list. Earlier documents may not include

low frequency-compatible products.

Also, avoid the frequency response trap. Frequency response is a technical specification for speakers

commonly found on data sheets and installation instructions. A typical value is 400 — 4,000 Hz, which

refers to the speaker’s ability to reproduce sound. Because 520 Hz falls within this range does not mean

the speaker is suitable for sleeping areas. Look for a statement that the device is UL 464 listed, or check

its nameplate label, or consult the appropriate compatibility list. If doubt remains, speak with the AHJ.

Low Frequency Signaling Handbook | Application Checklist 19

Application Checklist

If subject to the new NFPA 72 520 Hz requirement:

Horns and Sounder Bases

75 dB- at the pillow

520 Hz square wave tone output

UL 464 listed for 520 Hz signaling per nameplate label

Speakers

Preannounce tones, 520 Hz square wave


UL 464 and UL 864 listed for 520 Hz signaling per nameplate label

Documented in the system compatibility list as part of an end-to-end audio chain that is

listed to UL 464 and UL 864

Combination Horn-strobes

Combination horn-strobes are placed in accordance with the requirements for visible notification

appliances.


520 Hz square wave tone output

Placed no more than 16 feet from the pillow

UL 464 listed for 520 Hz signaling per nameplate

UL 1971 listed as a visible signaling appliance for the visually impaired per nameplate

Synchronized visible output if more than one device within the same line of sight

Minimum 110 cd light intensity when wall mounted more than 24 inches from the

ceiling

Minimum 177 cd light intensity when ceiling mounted or wall mounted less than 24

inches from the ceiling

Low Frequency Signaling Handbook | Application Checklist 20

Combination Speaker-strobes

Combination speaker-strobes are placed in accordance with the requirements for visible notification

appliances.

Pre-announce tones, 520 Hz square wave


UL 464 and UL 864 listed for 520 Hz signaling per nameplate

UL 1971 listed as a visible signaling appliance for the visually impaired per nameplate

Synchronized visible output if more than one device within the same line of sight

Placed no more than 16 feet from the pillow

Minimum 110 cd light intensity when wall mounted more than 24 inches from the

ceiling

Minimum 177 cd light intensity when ceiling mounted or wall mounted less than 24

inches from the ceiling



Control equipment, amplifiers



Employs a factory supplied 520 Hz square wave audio file

Low Frequency Signaling Handbook | Retrofits: When and Where 21

Retrofits: When and Where

520 Hz signaling requirements apply generally to new construction in specific sleeping areas. However, if

a retrofit requires extensive building renovations, the local AHJ or building standard may qualify the

project as new construction for life safety system purposes. Frequently, a life safety system overhaul,

such as the replacement of the main control panel, will also trigger new construction requirements.

Even if otherwise within the new requirement, low frequency signaling is considered optional for

installations begun prior to January 1, 2014. If desired, the switch can be achieved for non-voice audio

systems by simply adding or replacing standard horns with the low frequency variety. Low frequency

horns have a tendency towards higher current draw, so make sure to also reassess the system battery

and wiring capacities.

Voice audio retrofits require close consultation with the system compatibility list to ensure end-to-end

compliance with UL 464 and UL 864. Some manufacturers require the replacement of amplifiers and

other control equipment, as well as room side speakers. Others, such as Edwards, only need upgraded

speakers.

Low Frequency Signaling Handbook | Non-sleeping Areas: Is 520 Hz necessary? 22

Non-sleeping Areas: Is 520 Hz necessary?

The fire alarm code does not specify that the standard 3,000 Hz tone must be used outside of sleeping

areas. If desired, a 520 Hz signal could be used throughout a facility, as long as it meets sound pressure

level requirements.

One example for such use is in hallways outside sleeping rooms. While low frequency signals are not

required in these locations, installing two distinct tones (520 Hz and 3,000 Hz) in close proximity — even

when separated by a door — could compromise the signal’s efficacy. Installing low frequency horns in

the hallway would mitigate this risk.

For voice audio systems nothing precludes the playing of the same 520 Hz pre- and post- announcement

tone in the hallway over standard speakers as long as the sound pressure level is adequate, and the

speakers used in the adjacent sleeping areas are part of an end-to-end audio chain listed to UL 464.

Would building occupants be better served by 520 Hz signals everywhere? Should they become the de

facto standard for all emergency signaling applications? The answer, not surprisingly, is yes and no.

Installing UL listed 520 Hz signals can be more expensive. For horns and horn-strobes, there is a

significant jump in current draw requirements, which could increase system overhead. Battery

calculations and wire capacity also need to be taken into account. Battery life is one of the primary

reasons why 520 Hz is not currently required for residential smoke alarms.

Non-voice audio systems tend to be small applications such as a restaurant, small or medium-sized retail

space, or a small office. If the system is near a point where a supplementary power supply would be

required, then it probably wouldn’t be feasible to go with 520 Hz horns. But if there is room in the

system, and calculating the additional costs shows an insignificant overall increase, 520 Hz horns may

bring potentially better audibility to the application.

Low Frequency Signaling Handbook | Better Life Safety: Making the Right Calls 23

Better Life Safety: Making the Right Calls

An experienced life safety system designer knows that a large part of each project process is the cost-

benefit analysis. Even in a code-driven business there remains leeway to enable the system designer to

put his or her personal mark on the project. What they leave behind is a final product that’s built on a

mix of experience, technical knowhow and product knowledge.

The trick is making the right call for the project based on the needs of the building owner and the safety

requirements of its occupants. It’s not an easy task. With technology available today, there is virtually no

limit to the communications measures that can be put in place to save lives. But are all these measures

feasible? Are they practical? Will the builder owner accept the aesthetic look? Do they pass the cost-

benefit test?

When it comes to 520 Hz implementation, the only easy answers are the ones provided by the life safety

code. Strict compliance with all applicable requirements is, of course, required. However, an

experienced life safety system designer works not merely to comply with the code but to provide the

best possible protection for building occupants given the situation.

Whether 520 Hz finds application beyond sleeping areas will depend on your local AHJ, your client, and

your ability to think beyond the code. This is what distinguishes a good system designer from one that

really excels.


P/N 85000-0394, Issue 1

Contact us...

Email: [email protected] Web: www.est-fire.com

Edwards Detection and Alarm 1016 Corporate Park Drive Mebane, NC 27302

In Canada, contact Chubb Edwards... Email: [email protected] Web: www.chubbedwards.com

© 2015 United Technologies Corporation, Inc. All rights reserved. Specifications subject to change without notice. Edwards is part of UTC Building & Industrial Systems, a division of United Technologies Corporation.

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