Douglas Krantz - Technical Writer - Describing How It Works
Book: Make It Work - Conventional Fire Alarms

What are the Requirements for Off-Site Monitoring?

By Douglas Krantz | Life-Safety | 9 minutes of reading

What are the Requirements for Off-Site Monitoring?

What are the Requirements for Off-Site Monitoring?

Greetings Douglas

I have greatly enjoyed your site and learning from many of the newsletters that I have received from you. The one item that I am trying to understand better for my perspective is to fully understand the requirements once the signal reaches the panel and that transmission to the receiving station. I understand at a high level that there are different means of communicating that signal and the requirements to receive those.

Do you happen to know of any resources or available training that is out there to help me understand those requirements? That is one of the more confusing parts for me to read when I look through 72.

Thanks, A L, CFPS
Fire Marshal
Safety & Risk Management

A Fire Detection and Alarm System (FDAS) is a Life-Safety "Detect Fire and Warn People of the Fire" system. Communicating a fire alarm (Detect Fire) from the source of detection the fire to the occupants includes not just the occupants of the building (Warn People to get out), but it also includes communicating the detection of the fire to the fire department (Warn People to come and put out the fire, and possibly rescue people).

When doing this Detect Fire and Warn People of the Fire, Life-Safety says that the fire alarm system should always work. Period.

OK, real life says there will be problems with the system; the system won't always work.

Reliability of every part of the fire alarm system is important. Problems with the fire alarm equipment (detectors, control panels, power supplies, etc.) can be reduced by having a third party (like UL, FM, CE, Etc.) test to make sure the equipment will work as advertised.

Whereas wire itself can be tested, wiring is harder to test because the wiring will be different in each building.

Self-checking of every part of the fire alarm system (Supervision) is an internal way for the fire alarm system to check and make sure that it is always working. If the fire alarm system detection and warning system stops working at any time, building owners will be notified on a timely basis to come and fix the system so it will "Detect Fire and Warn People of the Fire" again.

Redundancy is also an issue when a "timely basis" isn't good enough. When something goes wrong with the system, the detection and warning uses an alternate, or redundant, method detect and warn.

Also, because this is a Life-Safety system, the Fire Detection and Alarm System has to work even when there is a power blackout. If a fire starts after the power is blacked out, the FDAS system still has to Warn People (occupants) to get out, and Warn People (fire department) to come and deal with the fire.

Regulatory Changes

In the past, the NFPA has been able to specify the wiring methods used for Detection and Warning, combined with the method of supervising to make sure of continuous internal supervision used for Life-Safety. However, that has become very cumbersome; there are too many methods to communicate Detect and Warn, along with the required supervision (and new types are being added regularly) to try and regulate all of the specific methods.

The DACT - DACR (Digital Alarm Communication Transmitter - Digital Alarm Communication Receiver) was one of the earlier casualties of this regulation change. That method was based on copper wire being installed all the way to the phone company, and then to the monitoring company.

The concept is still there, but the reality isn't. That copper wire has been replaced most of the way from the alarm system site to the monitoring company's site with fiber optics. The battery backup is changed, and the signal being sent as pulsed AC signals may start and end on copper wire, the signal however is converted from analog to digital, and then from digital to analog. Most of the signal pathway is on fiber.

Rather than trying to regulate the "how to" method to make a reliable, redundant, supervised, and battery backed up FDAS, the NFPA decided to go with the "outcome" method that states:
  • What reliability is
  • What redundancy is
  • What internal supervision is
  • What backup power is


For communicating signals off site, we are longer working with just DC signals or pules of AC signals, we also have computer style data being sent. The type of signal and method of carrying the signal can also change from one form to another along the same pathway. It may start out as a pulsed AC signal (4+2), be converted to a digital signal riding on packets of data, and then converted back again.

The signals still go from one end to the other on a pathway. For the signals sent from the fire alarm control panel to the monitoring company, the pathway is often defined as Class C.

Basically, Class C uses handshaking for supervision, can have more than one pathway, and shows a trouble signal when there is a problem. The pathway from the transmitter to the receiver may change from copper wire to fiber optics and back, but rather than being concerned with whether there is copper wire or fiber, the NFPA is concerned with the reliability, redundancy, supervision, and backup power for the entire path.

The requirements for which type of fire alarm communication equipment to use is more one of having been tested, listed, and labeled than one of what kind of signal is sent. This leaves specifics to the manufacturers, the NFPA is there to make sure the system will function.

I know, this isn't quite the answer you were looking for, but I hope this helps you anyway.

Training on the System

No, I don't know of an actual training program out there. There probably is one, I just don't know about it. There is an alternative to a training program, though.

Recommended Reading

I really, really recommend purchasing the "NFPA 72 National Fire Alarm and Signaling Code Handbook". It has the complete official NFPA Code, and from the writers and editors of the NFPA Code, included are lots of explanations about what the Code means.

Basically, explaining what the fire alarm system should look like, the NFPA 72 Code itself is legal-talk; explaining what the NFPA means with its legal-talk, the Handbook has added comments (using terms that even I can understand) to help show what the Code means. They even use illustrations.

Yes, the Handbook is more expensive. However, to get an understanding of what is meant by the legal terms shown in the codebook, the added explanations are worth much more than the extra expense.

The Handbook is available on the official NFPA website ---

Douglas Krantz

Mr. Krantz

Thank you so much for this information! This is a great help, and I really appreciate the insight from your response. I'll be sure to pick up a copy of the handbook and dive into the content a bit more to better get a handle on these items.

Thanks again! And I look forward to keeping up with the blog!

Thanks, A L, CFPS
Fire Marshal
Safety & Risk Management
Life Safety
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