Do fire alarm horns have to be synchronized?

Since 1996, NFPA 72 has required the use of the temporal 3 pattern for the audible fire alarm signal. NFPA 72 Chapter 18.4.2.3 requires the standard temporal 3 evacuation signal to be synchronized within a notification zone. As an example, a zone would be the devices in an apartment corridor. Each apartment would also be a zone. If you have multiple sounders in an apartment, those would need to be synchronized together, but not necessarily with the corridor horns.

Horn synchronization requirements should not be confused with epileptic seizure concerns that come from the ‘disco effect’ of non-synchronized strobe lights. The synchronization of audible patterns allows for clarity of signal and wouldn’t trigger an epileptic seizure, but non-synched audible patterns create an echo effect that can be disorienting. I’ve heard the effect and it is surprisingly disorienting. So while the specific reason cited for audible synchronization may be mistakenly lumped together with visual synchronization, the intent is the same and required by NFPA 72.

As with strobes, if you put different manufacturers on the same fire alarm notification circuit, you lose the audible synchronization. So if apartment sounders are on the same circuit as the corridor sounders, nothing will synch if you mix manufacturers. Fire alarm panels can only be programmed to use a single synching protocol so you can’t synch per circuit if they all come from the fire panel. However, if the apartment sounders are strung together on a separate circuit than the corridor sounders, you may have options. If that’s the case:

• You could have the fire panel re-programmed to provide no synch protocol and install brand specific synching modules that the circuits pass through on their way out. You would put one brand in the units and a different one in the corridor. All devices on a single circuit have to match.
• The apartment sounder circuit(s) could be swung over to a separate power supply that could be installed to synch one brand and the fire panel would synch a different brand in the corridor.
• If none of your apartments have more than one sounder, they don’t have to synch so you could mix manufacturers if, again, they are on a different circuit than the corridor sounders.
• Bottom line: The corridor sounders have to be synchronized and the sounders in any apartment with more than one sounder have to be synched. Individual apartments don’t have to be synched with other apartments or the corridor. All notification devices on a single circuit have to be from the same manufacturer in order to have their signals synchronized.

Gamewell-FCI fire alarm systems can synchronize most fire alarm horn/strobe manufacturers. From sales to design to installation, Affiliated Fire Systems has the most experienced technical personnel in the Chicagoland area to get your project done right the first time and on time. Contact us to get a quote today.

Gene Rowe
NICET IV Fire Alarm Systems
Affiliated Fire Systems, Inc.
Downers Grove, IL