Solving the Mystery of Intermittent Fire Alarm Communication Failures

If you've ever tried to track down a problem, especially when you're seeking help from tech support, you know that "intermittent" makes matters far worse. Anything that doesn't reliably appear is harder to replicate, figure out, and eliminate.

A recent support call between a Digitize engineer, John Ermatinger, and a client is a great example we can use. It will give you a much better understanding about how to diagnose and resolve intermittent communication failures.

Let's take a look at some specific snippets now (I've included a fuller transcript later on). I'll walk you through each lesson that we gain by learning from John.

This is a diagram of a legacy fire alarm system that takes advantage of both legacy and new fire alarm system components, all reporting to a Digitize System 3505 Prism LX head end unit. As you can see in the diagram, the Prism LX is able to interpret a wide range of signals.

The Problem: Intermittent Communication Failures

The call begins with the client describing a recurring issue: intermittent communication drops between their fire alarm system's remote annunciator (RA) and its main control system.

Client: "For the past three, four weeks, we've been getting two error messages: '[site name] is down' and 'No D-LAN.' The errors pop up and disappear quickly, but it's driving us nuts."

This type of intermittent issue is tricky to resolve because, as we discussed, it appears sporadically and self-corrects before diagnostic tools detect it. Despite previous efforts - including replacing network switches and transitioning the system from Wi-Fi to a wired connection - the problem remained.

Handshakes in Fire Alarm Communication

Fire alarm systems (as with many other systems) often use periodic "handshakes" to confirm active communication between devices. John quickly identified this as a potential cause of the problem.

John: "The handshakes occur every 20–25 seconds. If the system misses two handshakes in a row - about 40-45 seconds total - it declares the link down."

You can see how important it is to understand how timing mechanisms work within a fire alarm network. The root cause could lie in either the system failing to send the handshake signal or the remote enunciator simply not receiving it.

Two Potential Culprits: Network Hardware and Compatibility Issues

The support call then shifted to the network hardware. The client mentions that their team replaced an older network configuration with a single 16-port switch, yet the issue remains.

John: "Is it possible the new switch isn't fully compatible? Some gigabit switches don't always work well with 10/100 devices."

This mismatch can cause occasional communication disruptions, especially in mixed-speed networks. Even though your switch may "support" 10/100Mbps, the slower traditional speeds are subjected to less development scrutiny in favor of the modern gigabit standard.

This is a detail that's increasingly overlooked during hardware upgrades.

IT-Department Collaboration: Monitoring and Diagnostics

Next, to further isolate the issue, John suggests leveraging IT resources to analyze traffic between the fire alarm system and the remote enunciator.

John: "If their IT people can put a sniffer on the two IP addresses, they could track the 'hello' signals. The system might think it's sending the handshake, but the data could be lost before it reaches the annunciator."

This collaborative approach demonstrates how IT teams and fire alarm technicians can work together to diagnose issues. By monitoring both ends of the network, technicians can determine whether the problem lies with the system's handshake transmissions or the enunciator's response.

This wasn't a reality in the earlier days of telegraph and dial-up fire alarms, but it's a reality with IP-based systems in 2024.

Software Challenges: Versioning and Buzzer Issues

This conversation also reinforces the idea that software inconsistencies may exacerbate some issues. The client mentions an outdated software version and a persistent buzzing sound triggered by "reconnect" events.

Client: "We had them put the error message out of service because the 'reconnect' buzzing was driving the dispatch team crazy."

John: "That buzzing issue was resolved in software version 3.30. We should double-check their current version and update if necessary."

Outdated software can include unexpected bugs, such as unnecessary error messages or delayed responses to handshake signals. Ensuring all devices run compatible and up-to-date software versions is essential to maintaining system stability.

(Also, notice how John's encyclopedic knowledge of Digitize software versions comes shining through here!)

Acknowledge the Complexity of Intermittent Issues

Intermittent issues, such as the ones described in this call, create special challenges. John highlighted the importance of on-site diagnostics:

John: "Intermittent problems are the hardest to solve. Ideally, we'd catch it in the act. Maybe they could set up a laptop to log data continuously or let IT track the network traffic over time."

By gathering data during the failures, technicians can identify patterns that might reveal the root cause. Continuous monitoring is especially useful in systems that experience periodic disruptions (but work perfectly fine the majority of the time).

Proposed Solutions and Next Steps

At the end of this support call, John outlined a step-by-step plan to address the issues:

1. Verify Network Compatibility: Confirm that the replacement switch supports 10/100 Mbps devices to ensure that the intermediary network infrastructure isn't the problem.
2. Monitor Network Traffic: Use diagnostic tools to track handshake signals between the fire alarm system and the remote enunciator. This can help determine whether the problem lies in transmission or reception.
3. Update Software: Upgrade to the latest software version (3.30 in this case with Digitize equipment) to eliminate bugs, such as buzzing and unnecessary error messages. This also ensures compatibility with modern network protocols.
4. Log Intermittent Failures: Set up a dedicated laptop or monitoring device to capture data during communication drops. This will provide valuable insights for further analysis.
5. Collaborate with IT: Engage the end user's (this might be your own) IT team to analyze network traffic and ensure proper routing of handshake signals.

Lessons Learned: Preventive Maintenance and System Updates

This scenario can teach you a lot about the importance of preventive maintenance and staying current with hardware and software updates. While intermittent issues can be challenging to resolve, you can solve them.

John's focus on diagnostics and IT coordination provides a general roadmap for addressing many possible system issues.

Whether you're dealing with legacy hardware, mixed-speed networks, or intermittent communication failures, using methodical troubleshooting will help you see the truth and resolve the problem.

This Call Transcript Shows You What Good Support Looks Like

In this (abridged) call transcript, which I've referenced several times already, you can see a great example of what effective technical support should be. Take a second look, thinking about whether you get this level of support from your suppliers:

Client: "The [site name] has been dropping intermittently for weeks. We get two error messages: '[site name] is down' and 'No D-LAN.' It only drops briefly, but it's driving everyone nuts."

John: "What troubleshooting steps have you tried so far?"

Client: "We replaced the Wi-Fi connection with a direct wired connection and swapped two small switches for one 16-port switch. That seemed to help for a couple of days, but then the issue came back."

John: "The handshakes between the system and the annunciator happen every 20–25 seconds. If two handshakes are missed—about 40–45 seconds—it declares the link down. Could the new switch be causing compatibility issues? Some gigabit switches don't always work well with 10/100 devices."

Client: "I'll double-check that the switch supports 10/100."

John: "Have your IT team monitor the network traffic. They could use a sniffer to see if the handshake signals—'hello' messages—are being sent and received properly. Sometimes the system thinks it's sending the signal, but it might not be making it to the annunciator."

Client: "Good idea. I'll ask them to set that up. Maybe we can capture what's happening during a failure."

John: "Exactly. If they monitor both IP addresses, they'll see whether the issue lies in the system not sending the handshake or the enunciator not responding. The data footprint is small, so it won't overwhelm their network."

Client: "We've also been having an issue with buzzing during reconnect events, and the error messages are really annoying."

John: "The buzzing issue was resolved in software version 3.30. Do you know what version they're running?"

Client: "It's been a while since we updated. I'll check."

John: "Let's confirm that and update their software if needed. It'll not only fix the buzzing but also eliminate unnecessary error messages."

Client: "What about intermittent failures? They're so hard to track."

John: "Intermittent issues are always tricky. Ideally, you'd capture the problem in real time. Could they set up a laptop or monitoring device to log data continuously? That way, we can analyze the files when it breaks."

Client: "I'll ask IT if they can help with that."

John: "Great. Let's also verify that the system's switch is compatible with 10/100 Mbps devices. A mismatch could cause occasional disruptions."

Client: "Since replacing the switches, the issue went away for a few days but then returned."

John: "That suggests the switches might not be the root cause. Could you also confirm the switch's compatibility and monitor its performance over time? We've seen cases where switches work for a while and then fail intermittently."

John: "Once IT captures the network traffic, they'll be able to tell who's 'at fault.' Sometimes the system sends the handshake, but the enunciator doesn't respond—or vice versa."

Client: "Sounds like we're putting the system through a lie detector test."

John: "Exactly—like Maury Povich. We'll find out who's telling the truth."

Client: "What's next?"

John: "Here's the plan:

1) Verify the switch supports 10/100 Mbps.

2) Ask IT to monitor traffic between the system and annunciator.

3) Confirm and update the software to version 3.30 if needed.

4) Set up a logging device to capture intermittent failures.

Let's start with these steps and check back once you have more data."

Client: "Sounds good. Thanks, John."

John: "You're welcome. Let me know what you find, and we'll troubleshoot further if needed."

Conclusion: Empowering Technicians with Knowledge

Fire alarm systems are only as reliable as the networks that support them. When issues arise, a systematic approach - like the one demonstrated in this call - can uncover hidden problems and provide long-lasting solutions.

If your system is experiencing similar communication challenges, consider partnering with experts like Digitize to ensure optimal performance. From hardware upgrades to software updates and network diagnostics, our team can help you maintain a robust and reliable fire alarm system.

Call to Action

Ready to resolve your fire alarm system issues? Contact Digitize today to learn more about our cutting-edge solutions and expert support. Call 1-800-523-7232 or email info@digitize-inc.com. Together, we'll keep your systems running smoothly and reliably.

Andrew Erickson

Andrew Erickson is an Application Engineer at DPS Telecom, a manufacturer of semi-custom remote alarm monitoring systems based in Fresno, California. Andrew brings more than 17 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and...Read More