1 Scope
NOTE This standard covers public address (PA) and paging systems that distribute audio for routine announcements, background music, general intercom, and zone-based paging across a building or campus. (1.1)
NOTE It applies to schools, universities, offices, industrial facilities, warehouses, healthcare campuses, correctional facilities, and transportation terminals where clear voice communication must reach occupants across multiple zones. (1.2)
NOTE The standard addresses both system families in current use, and the early architecture decision between them governs nearly every downstream selection. (1.3)
1.3.1The system shall be one of the following architectures: 70-volt constant-voltage analog distributed audio, IP-networked audio (VoIP/AES67/Dante), or a hybrid retaining a constant-voltage speaker backbone with an IP paging overlay.
1.3.2Equipment furnished under this standard includes master and remote paging stations, zone selectors, power amplifiers, pre-amplifiers, digital signal processors, loudspeakers, supervision hardware, rack infrastructure, and standby power.
NOTE The standard also defines the supervised interface by which a PA system yields priority to a fire alarm Emergency Communications System (ECS), but the ECS itself is specified elsewhere. (1.4)
NOTE What this standard does not cover (1.5)
- Life-safety voice evacuation and emergency mass notification initiated by a fire alarm control unit are covered by Mass Notification Systems and Fire Alarm Systems; NFPA 72 Chapter 24 Emergency Communications System requirements belong in those standards.
- Fire alarm initiating devices, annunciators, and listed fire alarm control units are covered by Fire Alarm Systems.
- Backbone cabling infrastructure, conduit fill, pathway design, and telecommunications and equipment rooms are covered by Structured Cabling.
- Distributed Antenna Systems for cellular and public-safety radio are covered by Distributed Antenna Systems.
- Security intercom and access-control intercoms at building entrances belong to the access control standard.
- Auditorium sound reinforcement and audio-visual presentation systems belong to a separate AV standard.
2 Referenced Standards
2.1Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
| Standard |
Title |
| NFPA 72 (2022) |
National Fire Alarm and Signaling Code (Chapter 24 Emergency Communications Systems; intelligibility and supervision) |
| NFPA 70 (NEC, 2023) |
National Electrical Code (Article 640 audio equipment; Article 725 Class 2/3 signaling circuits; Article 800 communications cable) |
| NFPA 101 (2021) |
Life Safety Code (occupancy-specific requirements that may mandate paging capability) |
| UL 1480 |
Speakers for Fire Alarm, Emergency, and Commercial and Professional Use |
| UL 2572 |
Mass Notification Systems (dual-use paging plus emergency notification) |
| ANSI/ASA S12.60-2010 (R2020) |
Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools |
| IEC 60849 (1998) |
Sound Systems for Emergency Purposes |
| IEEE 446 |
Recommended Practice for Emergency and Standby Power Systems for Industrial and Commercial Applications |
3 System Architecture
NOTE The architecture decision is the single most consequential choice in a PA project, and the brief's most common pitfall is specifying a constant-voltage analog system where the program actually needs networked paging across multiple buildings. (3.1)
NOTE A 70-volt analog system distributes audio as a constant-voltage signal from centralized rack amplifiers through passive loudspeakers, each fitted with a step-down transformer tapped at a chosen wattage; it is simple, robust, and the default for small-to-medium single-building facilities. (3.2)
NOTE An IP-networked system carries audio as packets over the data network to PoE zone controllers and addressable endpoint speakers, scaling cleanly across a campus and integrating with SIP telephony and unified-communications platforms, at the cost of dependence on the IT network. (3.3)
NOTE A hybrid system overlays an IP paging console and routing core onto an existing constant-voltage speaker backbone, which is the economical path when reusing legacy distributed-audio wiring while adding networked control. (3.4)
3.4.1Select the system architecture.
● 70-volt constant-voltage analog (centralized rack amplifiers, passive speakers)
○ IP-networked audio (PoE zone controllers, addressable endpoints)
○ Hybrid (constant-voltage backbone with IP paging overlay)
3.4.2For IP-networked or hybrid architectures, the audio transport protocol shall be coordinated with the network design so that the required VLAN, multicast, and QoS configuration is provisioned under Structured Cabling. AES67
Dante
Proprietary IP (manufacturer-native)
Not applicable (analog system)
NOTE Where an IP system is selected, the audio network and its supervision shall not depend on routing or services that the owner's IT group can change without notice to the PA system owner. (3.5)
3.5.1The PA system shall remain operable for in-zone local paging during a failure of the wide-area network connection between buildings.
4 Zone Configuration and Paging
NOTE A zone is an independently addressable group of loudspeakers, and the zone map is the contractual definition of which call stations reach which speakers; the brief flags that omitting a zone matrix causes the contractor to default to all-call only and selective paging never works. (4.1)
4.1.1The system shall provide the number of independently switchable speaker zones scheduled for the project.
4.1.2The system shall support all-call paging that addresses every zone simultaneously.
4.1.3The system shall support selective paging to any single zone and to engineer-defined zone groups.
4.1.4A zone matrix identifying every call station, the zones it may address, and each zone's grouping shall be furnished, and zone-to-speaker assignment shall follow that matrix. zone matrix and speaker-zone plan NOTE Priority among audio sources determines which announcement is heard when two sources contend, and a documented priority order prevents a background-music source from masking a live page. (4.2)
4.2.1Live paging shall take priority over background music and over any automated or scheduled audio source.
4.2.2A fire alarm Emergency Communications System input, where present, shall override all PA sources, as required by the Fire Alarm Interface section.
4.2.3The default source priority, highest to lowest, shall be as configured below.
ECS override / live all-call page / live zone page / scheduled announcement / background music
Live all-call page / live zone page / scheduled announcement / background music (no ECS)
5 Paging Stations and Consoles
NOTE Master call stations, zone selectors, and remote microphones are the operator interface, and their type is selected to match the staff that will use them; a touchscreen IP console suits a campus dispatch desk, while a simple keypad microphone suits a single front office. (5.1)
5.1.1A primary paging station with microphone, zone selection, and all-call capability shall be furnished at the location scheduled. primary paging station location 5.1.2Each paging station shall provide a press-to-talk control and a visual ready/busy indication so the operator knows when the channel is live.
5.1.3Select the primary paging station type.
● Desktop keypad paging microphone (analog)
○ Wall-mount paging microphone (analog)
○ Touchscreen IP paging console
○ Telephone-access paging interface (dial-in from any extension)
5.1.4Specify the quantity of remote paging stations.
NOTE A telephone-access paging interface lets staff page by dialing an extension, but the brief warns that analog dial-access interfaces may not work across SIP trunks without an analog terminal adapter; PBX compatibility must be confirmed before selection. (5.2)
5.2.1Where a telephone-access paging interface is furnished, its compatibility with the facility telephone system, including any SIP-to-analog adaptation required, shall be confirmed in writing before rough-in.
6 Amplifiers and Signal Processing
NOTE Amplifier sizing is driven by the summed loudspeaker tap load plus headroom; the brief's pitfall is specifying amplifiers at 100% of the calculated tap load, which leaves no margin for program peaks and shortens amplifier life. (6.1)
6.1.1Each amplifier shall be sized so that the connected continuous loudspeaker tap load does not exceed 80% of the amplifier's rated continuous output.
6.1.2Specify the per-zone amplifier continuous output rating.
6.1.3Total harmonic distortion shall not exceed the specified maximum at rated output.
6.1.4The amplifier frequency response shall meet the specified passband for the program content the system carries.
● 100 Hz to 10 kHz (voice-grade paging)
○ 50 Hz to 20 kHz (music-capable)
NOTE Amplifier redundancy protects against the loss of an entire zone when a single amplifier fails, and N+1 backup with automatic failover is standard practice for systems serving large occupant loads or critical facilities. (6.2)
6.2.1Select the amplifier redundancy scheme.
● No redundancy (one amplifier per zone)
○ N+1 backup amplifier with automatic failover
NOTE A digital signal processor conditions the audio for each zone, and built-in equalization, delay, automatic gain control, and feedback suppression are what make a marginal room intelligible rather than merely loud. (6.3)
6.3.1The system shall provide per-zone digital signal processing with at least parametric equalization and level control.
6.3.2Select the additional DSP functions required.
☑ Parametric/graphic equalization (per zone)
☐ Delay compensation (loudspeaker time alignment)
☑ Automatic gain control
☐ Feedback suppression
☐ Ambient-noise-sensing automatic level control
7 Loudspeakers and Power Distribution
NOTE Loudspeaker type and mounting are selected for the space: recessed ceiling speakers for finished offices and classrooms, pendant speakers for open high-ceiling areas, and horn or compression-driver speakers for warehouses, loading docks, and outdoor areas where ambient noise is high and coverage distances are long. (7.1)
7.1.1Select the predominant loudspeaker type for the project.
● Recessed ceiling speaker with back can
○ Surface-mount ceiling/wall speaker
○ Pendant speaker
○ Horn / compression-driver speaker
○ Line array (high-ceiling or reverberant spaces)
7.1.2Loudspeakers shall be listed to UL 1480 for commercial paging use.
7.1.3Loudspeakers installed in air-handling plenums shall be furnished with a listed plenum-rated back enclosure.
NOTE The constant-voltage distribution level and the per-speaker tap wattage together set how much acoustic power each speaker delivers; 70.7 V distribution with a 1 to 2 W tap is the 80% case for classrooms and offices, while industrial and outdoor speakers are tapped much higher. (7.2)
7.2.1Select the constant-voltage distribution level.
● 70.7 V (standard commercial/institutional)
○ 25 V (small systems)
7.2.2Specify the nominal per-speaker tap power for the predominant space type.
0.25 W (quiet office, background music)
0.5 W
1 W
2 W
4 W
8 W (loud industrial / outdoor)
NOTE Outdoor and wet-location speakers fail early when generic indoor housings are used; the brief calls out that horn speakers on docks, fields, and parking structures need rated enclosures and UV-stable housings. (7.3)
7.3.1Loudspeakers installed outdoors or in wet, washdown, or high-humidity locations shall be rated to at least the specified enclosure standard with UV-stable housings.
○ IP55
○ IP66
○ NEMA 4
○ NEMA 4X
● Not applicable (no outdoor/wet locations)
NOTE Loudspeaker placement and spacing set whether coverage is even or patchy; the brief notes that 6 m on-center is the default for ordinary 8 to 10 ft ceilings, and that HVAC diffuser locations must be reconciled with speaker locations to avoid ceiling-conflict RFIs. (7.4)
7.4.1Specify the nominal ceiling-speaker spacing on center for the predominant ceiling height.
7.4.2Loudspeaker locations shall be coordinated with the reflected ceiling plan and with mechanical diffuser and lighting locations before permit, and conflicts shall be resolved on a coordinated ceiling layout. reflected ceiling plan with speaker locations 8 Cable and Power Distribution Infrastructure
NOTE Paging wiring is governed by two different NEC articles that apply in the same installation, and the brief stresses keeping them distinct: Article 640 covers the audio equipment power wiring and grounding, while Article 725 and Article 800 govern the low-voltage signal and communications cable. (8.1)
8.1.1Loudspeaker signal circuits shall be installed as NEC Class 2 circuits limited to 100 VA and 30 V where the constant-voltage level and load permit.
8.1.2Cable run in air-handling plenums shall be plenum-rated CL2P or CL3P per NEC Article 800.
8.1.3Speaker-circuit conductors shall be sized so that loop resistance does not exceed the loudspeaker manufacturer's stated limit, typically less than 10% of the total connected load impedance.
8.1.4Select the minimum speaker-circuit conductor size.
○ 18 AWG (70 V runs up to 50 ft)
● 16 AWG (standard for longer runs)
○ 14 AWG (long runs / high tap loads)
NOTE Hum and noise complaints on constant-voltage systems are almost always a grounding or shield-termination defect rather than an equipment fault, so the rack ground and shield discipline must be specified rather than left to the installer. (8.2)
8.2.1Equipment racks shall be bonded to a dedicated technical ground per NEC Article 640.
8.2.2Cable shields shall be terminated at one end only, in a consistent scheme documented on the riser, to prevent ground loops.
9 Standby Power
NOTE Standby power keeps paging available through a normal-power outage, and the required backup duration depends entirely on whether the PA system also serves a life-safety function; the brief sets 15 minutes for routine paging but 24 hours where the system serves an NFPA 72 ECS function. (9.1)
9.1.1The system head end, amplifiers, and call stations shall be supported by standby power for at least the scheduled backup duration.
○ 15 minutes (routine paging)
● 4 hours
○ 24 hours (PA serves NFPA 72 ECS function)
9.1.2Select the standby power source.
● Dedicated PA system UPS
○ Shared facility UPS
○ Facility standby generator with ride-through UPS
9.2The UPS supporting the amplifier room shall be sized for worst-case simultaneous all-call output, not merely idle draw, in accordance with IEEE 446.
NOTE Standby power sizing for the amplifier room follows IEEE 446 guidance; the UPS must support full simultaneous all-call load, not merely idle draw. (9.3)
10 Intelligibility and Coverage
NOTE Intelligibility, not loudness, is the measure of a usable paging system, and the brief insists that specifying an STI-PA target without requiring a post-installation measurement leaves the owner no remedy for a system that is loud but unintelligible. (10.1)
NOTE Speech Transmission Index (STI-PA) quantifies how much of speech survives the room's noise and reverberation; NFPA 72 requires STI-PA at least 0.45 for an ECS, and 0.50 is a sound target for general paging. (10.2)
10.2.1The system shall achieve the specified STI-PA value at no less than 90% of designated listening positions in each zone.
0.40.7
Default: 0.5 STI-PA
10.2.2Paging audio shall produce a sound pressure level of at least the specified minimum at the listener, measured 1.5 m above finished floor.
10.2.3Paging audio shall be at least 10 dB above the measured ambient noise level in each occupied space, and at least 15 dB above ambient where the system serves an ECS function.
NOTE In schools, the acoustic environment is constrained by ANSI/ASA S12.60, and those background-noise and reverberation limits directly drive speaker count and tap selection because a reverberant or noisy classroom destroys STI before any amplifier can compensate. (10.3)
10.3.1In core learning spaces, the loudspeaker layout shall be designed to achieve the intelligibility target within a reverberation time not exceeding 0.6 s, per ANSI/ASA S12.60.
10.3.2Classroom paging design shall assume the ANSI/ASA S12.60 background-noise limit of 35 dB(A) HVAC-only ambient when selecting speaker gain and tap.
11 Supervision and Fault Monitoring
NOTE Supervision is what distinguishes a maintained system from one that quietly fails, and the brief treats line supervision as a core requirement: a cut or shorted speaker line, or a failed amplifier, must annunciate rather than be discovered the next time someone tries to page. (11.1)
11.1.1Each loudspeaker circuit shall be supervised for open-circuit and short-circuit faults, and a fault shall be annunciated at the head end.
11.1.2Each amplifier shall report a fault condition, including loss of output, to the head-end annunciator.
11.1.3Select the supervision scope.
☑ Speaker-line open-circuit monitoring
☑ Speaker-line short-circuit monitoring
☑ Amplifier fault monitoring
☐ Standby power / UPS fault monitoring
☐ Network link supervision (IP systems)
12 Fire Alarm Interface
NOTE The interface to the fire alarm system is the most commonly under-specified item in a paging project, and the brief makes clear that most institutional occupancies require the PA system to yield priority to the fire alarm ECS; failing to specify the handshake produces a late, expensive coordination RFI with the fire alarm contractor. (12.1)
NOTE When the PA system is the listed NFPA 72 Chapter 24 Emergency Communications System rather than merely interfaced to one, it leaves the scope of this standard: it must then be listed to UL 2572 and specified under
Mass Notification Systems, because a generic paging spec applied to a life-safety system will fail AHJ inspection.
(12.2) 12.2.1Where a fire alarm system is present, the PA system shall accept a supervised priority-override signal from the fire alarm control unit and shall mute or release all PA audio while that signal is active.
12.2.2Select the fire alarm interface method.
● Supervised dry-contact relay input
○ Serial integration
○ IP integration
○ None (no fire alarm system present)
12.2.3The fire alarm override input shall be supervised so that a fault on the interface wiring is annunciated.
NOTE Public address must not be the sole means of communication for persons with hearing disabilities; ADA and Section 504 require a visual path, which is coordinated rather than furnished here. (12.3)
12.3.1Audible paging shall be paired with a visual notification path, such as strobe or display tie-in, where required by the project ADA compliance plan, and that requirement shall be coordinated with Mass Notification Systems. 13 Submittals
13.1The Contractor shall submit the following action submittals for review before fabrication or ordering:
- Product data for amplifiers, DSPs, paging stations, loudspeakers, and supervision hardware
- Shop drawings showing the system riser, zone matrix, and speaker-circuit loading calculations
- Loudspeaker coverage and intelligibility design calculations, including predicted STI-PA
- Standby power sizing calculations
- UL 1480 loudspeaker listings and, for dual-use systems, UL 2572 system listing
☑ Product data (amplifiers, DSP, stations, speakers, supervision)
☑ Shop drawings (riser, zone matrix, circuit loading)
☑ Coverage and STI-PA design calculations
☐ Standby power sizing calculations
☑ UL 1480 / UL 2572 listing documentation
13.2The Contractor shall submit the following closeout submittals before final acceptance:
- As-built riser and zone matrix reflecting installed conditions
- Operation and maintenance manuals
- Field test reports, including the intelligibility sweep and fault-simulation results
- Operator training records
☑ As-built riser and zone matrix
☑ Operation and maintenance manuals
☑ Field test reports (intelligibility, SPL, fault simulation)
☑ Operator training records
14 Quality Assurance
NOTE Quality assurance pins responsibility for a system whose performance is only proven after installation, so the standard requires qualified installers and, for dual-use life-safety systems, a dedicated commissioning agent as the brief warns. (14.1)
14.1.1The installing contractor shall be trained and authorized by the equipment manufacturer for the furnished system.
14.1.2Where the system serves a dual-use paging and emergency-notification function, a qualified commissioning agent independent of the installer shall verify NFPA 72 and UL 2572 compliance.
15 Factory and Field Testing
NOTE Testing is split between the factory, which proves the equipment works before it ships, and the field, which proves the installed system meets intelligibility and supervision requirements in the actual rooms. (15.1)
15.1.1Rack equipment shall undergo factory power-on burn-in before shipment.
15.1.2Speaker-line supervision shall be tested at the factory before shipment.
15.1.3An all-call and zone-select functional test shall be performed at the factory before shipment.
15.1.4A full field intelligibility sweep shall be performed with an STI-PA meter at each zone, and results shall meet the specified intelligibility target.
15.1.5Sound pressure level shall be measured at representative listening positions in each zone and shall meet the specified minimum SPL.
15.1.6Open-circuit and short-circuit faults shall be simulated on each speaker zone, and each shall annunciate at the head end.
15.1.7Where a fire alarm interface is present, the priority override shall be demonstrated to mute or release all PA audio while the override is active.
16 Installation
NOTE Installation requirements protect the design intent through construction, where the recurring failures are ceiling conflicts, missing plenum ratings, and grounding shortcuts. (16.1)
16.1.1Loudspeakers shall be installed at the coordinated locations and at the spacing required to achieve the specified coverage and intelligibility.
16.1.2All cable run in air-handling spaces shall carry the required plenum rating, and substitutions shall not be installed without engineer approval.
16.1.3Rack equipment shall be installed with the technical grounding and shield-termination scheme specified.
16.1.4Ground continuity shall be verified before energization.
16.1.5Outdoor and wet-location speakers shall be installed with their rated enclosures intact and with drip loops and sealed entries appropriate to the location.
17 Warranty
NOTE The warranty obligates the manufacturer and installer to stand behind the system through its early service life. (17.1)
17.1.1The system shall be warranted against defects in materials and workmanship for the specified period from the date of substantial completion.
○ 1 year
● 2 years
○ 3 years
18 Spare Parts
NOTE Spare parts let the owner restore service without waiting on procurement for the components most likely to fail or be damaged. (18.1)
18.1.1The Contractor shall furnish the scheduled quantity of spare loudspeakers matching each installed type.
18.1.2The Contractor shall furnish at least one spare amplifier module of each installed rating where N+1 redundancy is not provided.