© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 1
General Public Address and Intercom System
Design Guidelines
Rev 2016-1.01e
This guide provides general guidelines for designing public address and
intercom systems. The document begins at a very basic level and is
intended to assist novice designers.
In addition to this document, we encourage you to review our Best
Practices and General Troubleshooting Procedures guide.
We also offer additional resources for K12 schools such as a design
questionnaire and a market specific design/installation document,
We strongly encourage you to check for document updates often by
following the update link found in the footer.
This Document Is Intended To Be Viewed In PDF Format
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 2
Table of Contents
INTRODUCTION ...................................................................... 3
GETTING STARTED .................................................................. 4
SPEAKER CHOICES ......................................................................... 4
TECHNOLOGY CHOICES ................................................................... 6
DESIGN BY LOCATION .................................................................... 6
PLAN FOR GRANULARITY ................................................................ 6
SYSTEM POWER ........................................................................... 7
CHOOSE CONTROL EQUIPMENT ....................................................... 7
CLOCKS CHOICES .......................................................................... 9
VERTICAL MARKET FEATURES ............................................... 12
K12 SCHOOLS ............................................................................ 12
HIGHER EDUCATION .................................................................... 12
COMMERCIAL/INDUSTRIAL ........................................................... 13
GOVERNMENT/MILITARY ............................................................. 13
HEALTHCARE .............................................................................. 14
TRANSPORTATION ....................................................................... 14
DISCLAIMER ......................................................................... 15
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 3
Introduction
Public address systems became increasingly popular throughout the 20th century. The
industrial revolution led to large scale manufacturing facilities with hundreds, if not
thousands, of employees. Maintaining efficiency of such large scale operations required
the ability to locate key individuals rapidly and communicate to the masses
instantaneously. The only logical solution was a facility wide speaker system.
From those early roots has grown an industry dedicated to internal communications.
Systems have evolved from the old fashioned centrally amplified, microphone actuated
public address systems, to multimodal telephone based systems that utilize integrated
circuits, microprocessors and data network connectivity.
Today’s internal communication systems are comprised of both primary and secondary
communication devices. Primary devices provide instantaneous communication that
requires no action on the part or the message recipients. Even today, primary alerting is
best accomplished with a facility wide speaker system.
Secondary communication devices require the user to take some action or to be
prepared to receive the message. Examples include social media, text messaging and
e-mail.
Today, both primary and secondary communication systems can work in tandem.
Modern public address systems are designed not only for general announcements, but
for emergency notification. They often feature both one way and two way
communication and supervision to insure their availability in crisis situations.
Under microprocessor control, modern public address systems allow users to
dynamically choose message destinations and feature both live voice and prerecorded
audio capabilities.
Modern public address systems save money and lives.
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 4
Getting Started
Speaker Choices
There are many speaker styles available.
Ceiling speakers spaced at no more than twice the ceiling height are the best choice for
even sound coverage in interior areas. When following this rule, coverage per speaker
is simply the square of the spacing. For example, with 8 foot ceilings, spacing between
speakers would be 16 feet and each would cover 82 or 256 square feet. If working in
meters, then the units simply change to meters and meters2.
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 5
In critical noisy areas, like airport gate areas, space ceiling speakers at the ceiling
height.
The first and last rows of ceiling speakers should begin at half the spacing distance from
adjacent walls.
Wall speakers should only be used in small interior areas where there will only be a
single speaker, or if the use of ceiling speakers is not an option.
Horns are typically reserved for use in exterior environments, harsh environments or
large, loud interior locations.
Audio coverage by speakers and horns is a function of mounting height and the area’s
ambient acoustic characteristics and noise level. Refer to the recommended spacing
chart below. Note that, for horns, the chart is based upon an 18 foot mounting height.
Talkback, or 2-way intercom capability, is an option with any style of speaker or horn.
Speakers or horns used as talkback intercom points are typically accompanied by a
separately mounted pushbutton (call button).
The button allows users to ring a telephone. Once the telephone is answered, a
bidirectional connection is established with the talkback intercom point.
Talkback is an automatically switched, hands free connection and does not require
push-to-talk. The talkback conversation is terminated when the telephone terminates
the call.
Talkback intercom points are very common in classrooms, hospital operating rooms,
elevators, building entrances, medical examination rooms and car dealership mechanic
bays.
Robust versions of talkback intercom points, known as emergency call stations or help
points, are available in many forms and include one or more call buttons. These are
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 6
commonly used in parking garages, parking lots and any public space where immediate
assistance might be required.
There are many options for emergency help points such as integrated cameras, strobes
and light beacons for easy identification.
Technology choices
Before integrated circuit technology, all speaker systems used old fashioned
25/70.7/100 volt amplifiers and heavy gauge shielded wire. While old fashioned central
amplifiers are still used today, a more common approach allows the use of small gauge
UTP and self-amplified or IP based technology.
Self-amplified or IP based technologies allow for easy installation, functional versatility,
large scale deployment, and remote maintenance. UTP based systems are always the
best choice for large, busy facilities due to the fact that they inherently support many
simultaneous announcements and/or talkback intercom conversations.
Old fashioned centrally amplified systems are restricted to one broadcast per central
amplifier at any given time.
Design By Location
When designing a public address or intercom system for larger facilities, separate the
facility into logical sub divisions by floor and/or by function. Plan dedicated cabling and
other support products such as power supplies and network switches for each
subdivision.
Doing so will facilitate future maintenance and will provide the granularity to tailor
announcement recipient areas as the owner dictates.
Plan For Granularity
When planning the cabling speakers/horns in a facility, connecting them all on one
looped cable pull (even if feasible) limits you to one zone of audio. All audio will go to all
speakers due to the common cabling. Inversely, if you connect each speaker on its own
cable all the way back to the main equipment, then speakers/horns may be easily
configured in any future combination desired. In most installations, a wiring plan
between these 2 extremes is best. Loop speakers in common areas (multiple hallways,
restrooms, etc.) that will always receive common general announcements. Use
dedicated cables for speakers in areas that will likely require area specific audio or
omission from general announcements (classrooms, boardrooms, each floor, lobby,
etc.)
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 7
System Power
Valcom Self Amplified Speakers and some Valcom Controllers are rated in Valcom
Power Units (VPU). Products that require power have a negative VPU rating and
products that provide power (power supplies and some controllers) have a positive VPU
rating. The resulting sum of the VPUs in any particular location must simply be => zero.
It’s simple addition and subtraction, no complex power formulas are required. Power
supplies are independent of speaker zones, so one supply can power speakers in many
zones. VoIP speakers are PoE powered and do not require separate power supplies.
Refer to the published network requirements.
Choose Control Equipment
In the process of designing your cabling to allow for granularity, you will most likely have
considered the “zoning” required for the facility and which locations will be included in
each zone. Properly configured individual zones can always be combined into larger
groups, like all call, in system programming.
A paging zone is simply a combination of speakers and horns that will receive
announcements simultaneously. Zoning is usually dictated by area functions and
commonality. Usually whole floors of multi-story facilities are considered a zone with
sub zones further dividing the floor. Individual buildings are typically zones as are
outside areas.
K12 schools are by far the most granulized facilities with each classroom being a zone
(called a station since it will be feature talkback capability), each grade level being a
zone, each floor being a zone, etc.
There is no limit to the number of stations or zones in a modern public address/intercom
system.
The choice of using VoIP or analog equipment for the main control and audio
distribution is dependent upon many factors.
a) The preference of the owner
b) The size of the system
c) The number of sites included in the system
d) The feature set required
e) Initial budget
f) Desire for long term cost savings
Often, solutions involve both VoIP and analog components.
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 8
Typical system features include:
a) Telephone paging
a. Multiple access paths. One per potential simultaneous voice
page/intercom call. For each path:
i. You can use an FXO port from your phone system
ii. You can use a SIP identity from your VoIP phone system
iii. You can use a dedicated telephone
b) Scheduling
a. Shift change tones
b. Class change tones
c. Automated announcements
d. Music
c) WAV file storage and control
d) Clock synchronization control
e) Emergency messaging
f) Microphone access
g) Remote management
h) Text To Speech
Additional advanced system features include:
a) Automatic door/gate control
b) Graphical “point and click” message delivery
c) Facebook posts
d) Twitter Posts
e) Website Posts
f) LED Sign messaging
g) Offsite access via telephone line
h) Speaker supervision
i) Text To Speech
j) Automatic Messaging from monitored CAP, RSS, ATOM feeds
k) IP Camera Integration
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 9
Clocks Choices
It may seem odd to discuss clocks in a document concerning public address system
and intercom design, but it’s really not odd at all.
Just as a properly designed public address system is essential for communicating with a
large number of people, a synchronized clock system is essential for keeping those
people on schedule. Synchronized clocks are clocks that always show the same time.
This is very important in order to coordinate the activities of personnel and students.
Without a single time standard, people have no way to know when it’s time to begin and
end the work day, attend meetings or, in the case of students, assemble for classes.
Many public address systems offer the ability to synchronize clocks so that scheduled
audio may be broadcast when the clocks reach specified times. The use of shift or class
change tones along with synchronized clocks provides an audible notification for
listeners to keep on schedule. It’s very important that the audible notifications and
clocks are coordinated.
There are several clock correction methods that may be used:
Wireless
Wireless clock synchronization, as the name implies, is accomplished through radio
frequency transmission. The master clock or public address system’s integrated master
clock constantly broadcasts the correct time.
A superior system will use frequency hopping technology to avoid interference and will
feature the ability for clocks to rebroadcast any valid time correction signals in order to
propagate the correction signal throughout the facility. Wireless clock systems that do
not include signal repeaters in each clock may require periodic renewal of a site FCC
license and expensive stand-alone signal repeaters.
Wireless correction is a very good choice for any facility and significantly reduces the
cost of wiring.
Wired Clocks
Wired clocks may use old fashioned synchronous correction protocols or modern 2-wire
digital correction. New installations of wired clocks should always use modern 2-wire
digital correction as synchronous correction takes a significant amount of time to update
the clocks following time changes. 2-wire digital clock correction constantly provides
updated time information and corrects the clocks immediately when time changes or
after temporary facility power failures. 2-wire digital correction is maintenance free and
uses a single pair of Unshielded Twisted Pair wire.
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 10
Network Based/IP Clocks
Network based or IP clocks connect to a PoE network port. They are powered from, and
receive correction data from, the network switch. They obtain time from an NTP
(Network Time Protocol) server. These are a good choice for modern facilities that
choose to coordinate time between multiple networked systems with a maintenance free
solution. IP clock correction corrects the clocks quickly after time changes and, should
facility power temporarily fail, immediately upon restoration of the network.
Non IP Clock Power
Analog display wireless clocks are available with long life battery power or may be
powered with 24vdc over a single pair of Unshielded Twisted Pair wire. Wired digital
and analog display clocks are powered with 24vdc over UTP cable.
Display types
All analog display clocks are available in 16 inch (40.6 cm) and 12 inch (30.48 cm).
Digital display clocks are available with 2.5 inch (6.35 cm) or 4.0 inch (10.16 cm) digits.
Digital display clocks may have 4 digit displays for hours and minutes or 6 digit displays
for hours, minutes and seconds. 12 inch analog display or 2.5 inch digital display clocks
work well in offices, lobbies, break rooms and other small to mid-sized areas. 16 inch
display or 4.0 inch digital display clocks have high visibility and should be used in large
rooms and open common areas.
Mounting
All clocks are available in single sided wall mounted or double sided wall/ceiling
mounted versions.
Time Base
The time displayed on the synchronized clocks will only be as accurate as the time
provided by the master clock or public address integrated system master clock. All
modern systems use either NTP or receive time from GPS satellites; however, there is
no need to have both in one system as this simply adds unnecessary cost.
Spacing
16 inch (40.6 cm) clocks may be read from as far as 140 feet (43 meters)
12 inch (30.48 cm) clocks may be read from as far as 98 feet (30 meters)
2.5 inch (6.35 cm) clocks may be read from as far as 150 feet (45 meters)
4.0 inch (10.16 cm) clocks may be read from as far as 250 feet (76 meters)
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 11
Once you’ve selected the features you’ll need, the number and type of clocks, speakers,
horns and zones/stations you’ll need per area, a quick call to Valcom will result in an
equipment list for your job. Note that the accuracy of the equipment list will only be as
accurate and thorough as the information that you provide.
Basic Pre Call Checklist
Are you comfortable with your understanding of how the system will be utilized?
Do you have specific information of the capabilities, Input/Outputs, tap settings of
speakers, capacity of amplifiers, etc. of any existing equipment that will be reutilized?
Have you determined an adequate zoning plan so that announcements can be
broadcast/displayed to target audiences without disrupting everyone?
Have you determined how you’d like to deploy announcements? Speakers/Horns,
Computer pop up alerts, LED signs, etc.
Have you given thought to the type of system you’d like? IP, analog, both
Have you determined the number and type of speakers, horns, clocks and LED signs
required on a per area basis?
Have you selected speaker/horn/clock/LED sign styles?
Do you know ceiling heights and type of ceiling for each area?
If areas have drop ceiling, do you know the dimensions of the grid?
Have you identified wiring closets in each area to accommodate support products such
as power supplies and network gateways?
Have you determined how and from where the system will be accessed?
Do you have information on the available FXO ports and SIP capability of the host
phone system?
Have you determined how many users may be using the system simultaneously?
Have you determined an appropriate feature set for the facility?
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 12
Vertical Market Features
Common features for particular vertical markets include:
K12 Schools
General and emergency level zoned paging to provide information and locate personnel
A system of synchronized clocks and bell tones to manage student class changes
Class Change Schedules
Talkback communication and call buttons per classroom
Automatic Scheduled Announcements
Countdown (to next class period) Clocks and clock correction
Control Facility Environmental Systems
Lockdown and lockdown confirmation
Multi-Language systems
Panic Buttons
Retrofit systems that reuse existing speakers and cabling
Classroom Sound Reinforcement
Automatic music control for class change periods
Higher Education
General and emergency level zoned paging to provide information and locate personnel
A system of synchronized clocks for a single time standard
Dorm room panic buttons to alert campus police
Campus Information System
Emergency IP Cameras
Touchscreen Incident Management
Incident mapping
Incident Reporting System
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 13
Staff/Student/Parent Alerts and Notifications
Personal communication device alert
PSAP Alerting/911 Call Alert
Commercial/Industrial
General and emergency level zoned paging to provide information and locate personnel
A system of synchronized clocks and shift change tones for a single time standard
Automated messaging from facility processes/machines
Automatic System Tests
Automated Announcements Triggered From the Fire Alarm
Forklift messaging and notification
Loud Ringing Phone Call Notification over Speakers and Horns
Automatic Volume Adjustment for Fluctuating Ambient Noise Levels
OSHA Compliance
Shift Change Tones/management
Government/Military
General and emergency level zoned paging to provide information and locate personnel
A system of synchronized clocks for a single time standard
Airport Crash System/Radio Integration
Base wide Communication
Speakers with Integrated LED Flashers For Alerts
Multi City/State systems
Secure Eavesdrop-Proof Speakers for Classified Information Areas/Meeting Rooms
Sound Masking for Privacy
Supervised/ Automatically Monitored Systems
Timed (Scheduled) music
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 14
Healthcare
General and emergency level zoned paging to provide information and locate personnel
A system of synchronized clocks for a single time standard
Hands Free Talkback Intercom In Operating Rooms
Area of Rescue Assurance
Button Launched Pre-recorded Coded Announcements
6 Digit Countdown Digital Clocks to Time Procedures
Digital Signage for Information
HIPPA Compliance
Site Wide Lullaby to Welcome New Births
Spot Sound Masking For Patient Privacy
System wide Paging
PC Pop Up Alerts
Transportation
General and emergency level zoned paging to provide information and locate personnel
A system of synchronized clocks for a single time standard
Ruggedized Help Points/Panic Buttons At Bus Stops And Train Platforms
Access Control
ADA Compliance
Automatic Emergency Information/Weather/Terrorist Act Monitor
Intercom to Dock Drivers/Gates
Automated Pre-Recorded Announcements
Acoustic Feedback Prevention
Scheduled and Manual Arrival/Departure Announcements
Announcements over Telephone Speakers
Strobe Activation
© 2016 Valcom, Inc. Roanoke, VA www.Valcom.com Check for Updates - https://goo.gl/wfNYHC Page 15
Disclaimer
Note that any applicable standards by official regulatory agencies or ANSI/TIA/EIA/IEEE
should always be observed. In the case of conflicting information, these standards shall
prevail.
The suggestions provided may or may not be suitable for your intended application.
Please consider this information carefully before incorporating it into your system
design. Valcom disclaims any responsibility for accuracy or completeness.
Valcom is not responsible for the content found via hyperlinks within this document.
Content was evaluated and found appropriate and relevant at the time of publication.
This document supersedes all previous versions. Please check for updates at the
following URL - https://goo.gl/wfNYHC
Valcom, Incorporated
5614 Hollins Rd
Roanoke, VA 24019 U.S.A.
1-540-563-2000
Regular Business Hours are Monday – Friday
8:30 a.m. to 7:30 p.m.
Designed, Built and Supported In The U.S.A!
