Fire Alarm Pull Handle Tutorial & Buyer's Guide
By Andrew Erickson
September 5, 2022
As much as I read about the more complex aspects of fire alarm monitoring, none of that actually matters if you can't get an alarm trigger in the first place. That's why you can't afford to ignore parts of your system as simple as a fire alarm pull station.
As strange as it might sound in 2022, the humble manual pull station still has a place in the modern fire alarm system. Just ask the City of Boston, where pull stations have seen continued use even in the smartphone age. For key municipal decision-makers there, the general public and a comprehensive set of pull stations on almost every street corner provide both speed and redundancy.
Dual Action vs. Single Action fire alarm pull stations
One set of terms that you're likely to come across while you're doing your shopping research is "dual action" vs. "single action" pull stations. When I was still fairly new in the fire alarm space, I found myself doing some research on this distinction myself.
As it turns out, my confusion stemmed from the fact that most fire alarm pull boxes that you see in the modern world are dual action. The design that you're likely to have seen most frequently involves two different actions in order to activate the fire alarm. An operator, which may be an employee or a member of the general public, simply needs to push in on a section above the handle before being able to pull down the handle.
The concept of dual action is very much like you may have seen in movies involving missile launches. To prevent inadvertent activation, you may have seen a clear plastic cover on top of a button. This is, obviously, to prevent a major function from being activated at a time when it should not.
Fire alarm pull stations operate on very much the same principle. If that handle gets pulled, a massive response in the form of emergency vehicles and first responders is going to occur. You wouldn't want that to happen without good reason.
Single action pull stations do not offer this extra measure of protection against false alarms. Because the cost of extra certainty is only perhaps a fraction of a second, dual action fire alarms have become the modern standard.
So, now we have a fire alarm that has been pulled. Remember, however, that a fire alarm pull means nothing without reliable telecommunications. The fact that a pull has occurred needs to go somewhere. But how?
Fire alarm pulls are traditionally transmitted using telegraph technology
Imagine a hypothetical scenario where someone has just pulled a fire alarm. That action means precisely nothing if there's nowhere for the alarm data to go. What's going to happen now that the alarm is been pulled? Who's going to be alerted? Is an audible alarm going to be sounded?
Over the years and decades, many different methods of transporting alarm events have been invented. To go back to the beginning, we literally go back to the telegraph age.
Traditional fire alarm pull stations, many of which are still used today, operate on the basis of a spring-loaded wheel. When the handle is pulled, the wheel is released in the spring begins to turn it. The spring has enough stored tension to turn the wheel about four times.
Each time the wheel goes around, notches in its edge transmit a short series of telegraph pulses. In most systems, each pull station is given a three-digit number (ex. "714"). Each pull station has a unique wheel with unique notches in it so that it can tap out its own unique number when activated.
Back at the central monitoring station, someone is waiting to receive the telegraph pulses and decode the identifying number of the pull station. In the modern age, you're more likely to see a computer than a human receive the message. Still, the principle remains the same. Telegraph data will be received, and that will indicate where the fire alarm is happening.
Today, you're not likely to find a modern system that includes telegraph taps unless the goal is to integrate with an existing legacy system.
Some pull stations use electrical contact closures
Aside from telegraph pulses, the next progression in technology was to use simple electrical contacts to transmit fire alarms. If you've ever flicked on a light switch, you understand this principle.
When a fire alarm pull station that is based on this technology is pulled, a computer on the far end detects that electrical continuity has changed. There now is or is not electrical flow, which is different than before. Home alarm sensors on windows and doors operate on the same principle.
What is distinct about fire alarms is the common use of a resistor on the line. In this way, you actually get more information that a traditional binary contact closure. Zero vs. a small amount vs. a large amount of electrical flow can be distinguished. These indicate whether you have a broken wire, a normal condition, or an active fire alarm.
Modern pull stations can include serial, Ethernet, or radio communication.
The continuous forward march of technology has given us many more options for transmitting fire alarms in the last few decades. For newer installations, you might see pull stations that are addressable in their communication with the fire alarm control panel (FACP). This might be via serial or ethernet.
Digitize also manufactures a fire alarm pull station that operates on the basis of radio technology. Wireless commit occasion is not without some challenges, but it does offer a massive savings in terms of infrastructure installation and is immune to wire damage during a fire.
Talk to expert to complete your fire alarm project faster
Life safety is very serious business. Fire protection technology really isn't overly complex, but you need the right knowledge and background to be able to make good decisions.If you need to understand how manual fire alarm initiating devices work, the engineers at Digitize have the experience and expertise that you need.
Give us a call to discuss fire alarm pull stations, central fire alarm monitoring servers, or anything else that you're trying to accomplish.
Call 1-800-523-7232 or email me at firstname.lastname@example.org
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 16 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and...Read More