Echoing Fire Signals Over IP: Solving the Bell Relay Problem Without Copper

There's a reason traditional fire bell tap-out systems have survived for more than a century: they're simple, reliable, and unmistakably audible. But what happens when the infrastructure those systems rely on no longer exists or can't be installed?

This is the exact challenge we faced when a client reached out with a seemingly impossible request. They were looking to recreate an audible bell tap-out sequence across a modern IP network - without compromising on timing, rhythm, or reliability.

In other words, the goal was to replicate the classic experience of "box number" rings at a second location, even when there's no wire pair to make it happen.

Let's explore how we arrived at a solution that does exactly that, and why this challenge is more common - and more solvable - than it might seem at first glance.

There's No Wire Path for Bell Relays

Anyone working in fire alarm systems knows that tap-out bells aren't just an old-school fire safety quirk. They're a mission-critical element in many municipal setups. From legacy firehouses to remote public safety buildings, the system often goes like this:

• A central fire alarm control panel (FACP) or coded pull station triggers a specific number of audible pulses on a bell.
• Firefighters, staff, or volunteers hear the ringing and count the pulses to determine which box has been activated.
• That box number correlates to a location, which is logged, paged out, or responded to accordingly.

It's low-tech, but it works. Reliably.

The problem is these bells rely on dedicated copper wiring. Typically, the panel connects to a bell or tap-out device via a simple wire pair, carrying the electrical pulses that trigger the sound. That model breaks down fast when:

• The buildings are no longer connected by wire.
• The infrastructure has been damaged or renovated.
• Running new conduit or trenching wire is too expensive, too slow, or just plain impossible due to physical barriers or historical restrictions.

That's the situation our client found themselves in. They have two fire-related buildings with no copper between them, and a very clear need to replicate those precise bell signals in both locations.

Standard Network Devices Aren't Enough

There are a lot of devices that can send information over a network. You've got IP encoders, audio relays, web-based control panels, and plenty of home automation tech that could theoretically send a "ring now" command from one place to another.

So, why not just use something off-the-shelf?

The answer comes down to rhythm.

The whole point of a tap-out system is that humans listen to it. The number, spacing, and cadence of the rings is the message.

If the timing is off by even a fraction of a second, the meaning becomes unclear. A three-ring sequence could be mistaken for two or four.

Most IP devices (even good ones) introduce just enough network latency or timing jitter to make these sequences unreliable. It might be okay for a buzzer, but not for a fire bell that's supposed to communicate something as specific as a box number.

Also, common IP-based audio solutions tend to:

• Send pulses immediately but out of sync, causing audible distortions.
• Miss short pulses, which are common in fast tap-out sequences.
• Fail to handle bidirectional echoing, which some systems need for redundancy or verification.
• Lack granularity in pulse resolution, meaning they can't preserve the typical 2–6 pulses per second with the right pause between sequences.

The challenge was clear: traditional IP solutions couldn't replicate the full functionality of a tap-out bell over a network - at least not without compromising reliability.

Use a Digitized Echo System with Real-Time Playback

To bridge the gap between legacy analog behavior and digital transmission, we needed to think differently.

Rather than attempt to transmit each pulse over the network in real time (and risk distortion), we:

1. Recorded the entire sequence of pulses as a unit.
2. Encoded it digitally into a simple integer representing the count and cadence.
3. Transmitted that digitized sequence over the LAN to a receiver.
4. Played it back locally with preserved timing - as if the pulses had been delivered directly by copper.

This idea formed the core of what became the Echo system: a sender-receiver device pair that listens to an existing bell output, digitizes and transmits the signal over IP, and faithfully reproduces it on the other side.

And we weren't just thinking about one customer. Once we sketched the design, we quickly realized how broadly this could apply across fire service applications.

How the Echo System Works: A Breakdown

The Echo system consists of two custom-built devices operating as a matched pair - one sender, one receiver. Here's what each one does:

Sender Box

• Input: Connects to any device that normally outputs to a bell box (such as a Prism LX).
• Detection: Monitors the pulses in real time.
• Encoding: Translates the number and spacing of the pulses into a digital format - essentially, an integer representing the tap-out pattern.
• Transmission: Sends the encoded message over a local area network (LAN) to the designated Receiver box.

Receiver Box

• Reception: Listens for incoming messages from the Sender.
• Decoding: Converts the digital signal back into an analog pulse sequence.
• Output: Triggers pulses onto a local wire pair, activating a connected bell box to recreate the original sound - rhythm and all.

Timing Preservation

The best part about this system is that timing isn't lost in the encoding. The playback includes the pauses and rhythm from the original signal. By buffering the sequence before playback and ensuring output only occurs once the full message is received, the system avoids the latency issues common in IP communication. It might be delayed by a split-second before it begins, but the sequence itself is essentially flawless once playback begins.

The result is a perfectly mirrored bell tap-out. It happens within a few seconds of the original ring, and is indistinguishable to the human ear from a hardwired system.

Technical Specs and Capabilities

Let's go under the hood for a second. The Echo boxes:

• Work in bidirectional pairs: Either unit can be configured as sender or receiver.
• Require LAN connectivity only: No need for special VPNs, proprietary software, or cloud platforms.
• Support granular pulse recognition: 2–6 rings per second (1/3 to 1/2 second timing), with high-resolution pause detection.
• Offer a web interface: For status monitoring, diagnostics, and future expandability.

Since these devices don't directly control fire suppression systems or activate alarms (they merely reproduce audible signals), they're often considered ancillary devices in most AHJ jurisdictions. Still, it's the responsibility of the system owner or contractor to confirm code compliance for their specific installation.

Solving the Legacy Tap-Out Conflict

In the field, this system was first used to solve a bell relay challenge where a fire station and an auxiliary building could no longer be connected via direct wire. The client had previously been told that no commercial solution existed - at least, not without thousands in development fees.

Recognizing the utility of the concept, we waived the standard custom development cost. We knew this wouldn't be the last time a municipal or industrial client needed tap-out bell replication without copper. The Echo system filled a clear gap in the market, one that no "universal relay" or IP paging solution had managed to fill.

Looking Ahead: More Echo, Less Copper

While this started as a one-off request, the Echo system is already being considered for future fire monitoring solutions and integrations. As more municipalities modernize their alarm infrastructure, the need for IP-based devices that honor legacy systems - rather than ignore or replace them - will continue to grow.

The Echo is just one example of how small innovations in the right places can solve big logistical headaches.

Need to Echo Bell Signals Over IP? Let's Talk

If you're trying to maintain or replicate traditional tap-out bell functionality across modern infrastructure, you're not alone.

Copper is going away and buildings are changing. However, the expectation for reliable, audible, code-compliant fire signaling hasn't changed.

That's where solutions like the Echo come in.

Want to discuss your specific layout, bell system, or integration needs? Whether it's a simple one-building relay or a multi-site expansion plan, we'd love to hear what you're working on - and see how we can help.

Call Digitize at (973) 663-1011 or email us at info@digitize-inc.com to start the conversation.