Why Clients Are Moving Away From 100mA Loops

By Justin Sagalow

November 18, 2022

copper cable

This is a spool of copper cable located underground. Telegraph-based alarm monitoring systems use cables like these to transmit alerts throughout a loop.

Digitize’s bread and butter is offering alternative solutions to completely replacing existing alarm monitoring systems. We purposely design our products to interface with different types of alarm signaling technology dating all the way back to the 19th century. With Digitize equipment, you can slowly replace outdated aspects of your system without ever having to pause its monitoring ability or take the system completely offline.

Those familiar with this blog will know that this is something we have written about several times in the past. Anyone who has read about our work with the University of Pennsylvania or our blog advocating for updating legacy fire alarm systems already knows that we are passionate about modernizing fire alarm systems that are at risk of failing. Our goal is to provide you with state-of-the-art alarm monitoring capability while helping you avoid expensive and inconvenient full-scale construction projects.

Today, we’d like to take a closer look at a very common type of legacy fire alarm system. Telegraph-based fire alarm monitoring systems that utilize 100 milliamp (mA) loops can be found all over the country. Many of these loops are quite old, and oftentimes, not properly maintained. Considering that the installation of some of the first 100mA loops in this country took place over 100 years ago, many of the telecommunications companies that originally laid them no longer exist. The ones that are still around sometimes have little incentive to perform continued maintenance on these loops.

Without proper maintenance, and sometimes even with proper upkeep, these old systems are at risk for failure. As we know from experience, the nature of these copper loops usually leaves them in jeopardy of having a single point of failure. A problem with a single cable can bring down an entire alarm reporting system.

The advantages and disadvantages of telegraph-based fire alarm systems

Despite their shortcomings, coded telegraph-based systems, or systems that use 100mA loops of copper wires, are still widely used in large cities throughout New England. Boston is one of the largest cities in the country that actively uses a 100mA loop-based telegraph fire alarm system. They actively maintain these copper loops and use an assortment of legacy and modern fire alarm monitoring technology to support and fortify their telegraph-based fire alarm system throughout the city.

Additionally, some of the largest underground transportation services in the United States use telegraph-based alarm systems consisting of 100mA loops of copper wires (although some are exploring moving towards Ethernet-enabled panels).

Telegraph fire alarm systems do have certain admirable qualities that explain why some municipal and transportation organizations are hesitant to rid themselves of them. When telegraph-based alarm reporting systems are fully functional, they are fast and dependable. They have stood the test of time when it comes to quickly and accurately relaying information without complication (assuming the system is in properly-working condition).

Many municipal organizations also admire the autonomy granted to them by using 100mA loops in their fire signaling systems. These systems do not require IT departments, Central Station services, network permissions, or any of the other roadblocks that come with implementing modern technology.

While we can appreciate the simplicity and freedom that comes with utilizing coded telegraph-based alarm signaling systems, we also know better than to overlook its obvious drawbacks.

subway work

This is a construction site for work being done on an underground transit line. These construction projects are expensive and intrusive, and can cause traffic and accidents in surrounding areas. Digitize offers custom alarm monitoring solutions to help clients avoid large construction projects.

As a company that promotes itself on being sympathetic to the budgets of its clients, we have to acknowledge that copper is notoriously expensive. Over the last 2 years, copper has reportedly hit an all-time high in value. In the event that existing cables need to be repaired or new cables need to be installed, the price of the wires themselves, compounded with the expenses required to access the cables and set up the necessary safety precautions for a construction site is more than enough of a deterrent for many to want to continue to pursue telegraph-based alarm monitoring solutions. This is without even mentioning the exorbitant fees that come with soliciting the services of a firewatch team to monitor the alarm locations while the alarm monitoring system is offline.

Copper wires themselves are also limited in the distances they can reach due to the nature of electrical telegraphy. When the radius of a loop is expanded, it increases the resistance on the cables. Eventually, additional cables will need to be installed to carry this load, which, as we addressed above, can be a very expensive, invasive and lengthy process.

As we’ve seen during our experience working with the University of Pennsylvania, copper cable-based alarm signaling systems are extremely accident-prone. A construction mishap, natural disaster, or even an above-ground car accident could be all that it takes to begin the much-dreaded copper cable 100mA loop excavation and restoration process.

Migrating to radio, Ethernet, or fiber panels

More and more often, we’re seeing clients that currently have coded telegraph-based fire alarm systems express interest in migrating to radio, Ethernet, or fiber panels. Some clients are put off by the vulnerable points and expenses of copper wiring, while others have expressed frustration in the decreasing frequency of services that are able to service these copper loops. After all, the more outdated this technique of signal communication becomes, the less maintenance services find it profitable to accommodate them.

Other clients are just interested in the forefront of alarm monitoring technology. They see the potential that radio, Ethernet and fiber panels offer, and are excited about companies like Digitize that want to explore the possibilities of alarm monitoring in the 21st century.


This is an image of a Digitize Muxpad II. The Muxpad II is a Data Gathering Module (DGM), which is a part of the Digitize System 3505 Prism LX™ Supervised Bidirectional Polling Alarm Monitoring System. It is used to monitor addressable fire alarm control panels (FACP).

Next week, we will take a closer look at radio, Ethernet, and fiber panels and explore each one of them in detail, along with why so many people are interested in migrating to them.

Update your fire alarm monitoring system today

If your telegraph-based fire alarm system utilizes a 100mA loop and you are thinking of migrating to radio, Ethernet, or fiber panels, we recommend that you reach out to us immediately. Updating your fire alarm monitoring infrastructure is also a great opportunity to take care of any other improvements simultaneously.

When you call your Digitize engineer, you can also talk through any opportunities for improvement that you have in mind. We’ll also ask you a few questions to check for updated system design opportunities you may not have considered.

Digitize is ready to speak with you about your upgrade at 1-800-523-7232. If you prefer, you can also email us at info@digitize-inc.com

Justin Sagalow

Justin Sagalow

Justin Sagalow is quite uniquely qualified for his Marketing Writer Position at Digitize. Arriving at Digitize with experience in law, finance, and editorial positions, Justin's skillset allow him to effectively communicate how best Digitize can address each client's individual needs. From his...Read More