Douglas Krantz - Technical Writer - Describing How It Works

How does the Panel Decide if a Signal is Alarm or Supervisory?

Supervisory is programmed into the system as the system is installed. If a signal is programmed as an alarm, the panel says "Alarm", if the signal is programmed as a supervisory, the panel says "Supervisory".

How does the Panel Decide if a Signal is Alarm or Supervisory?

Greetings Douglas,

I have question. How does the fire alarm control panel decide if a signal is an alarm, trouble, supervisory, or a monitor signal?

Thank you, FT

The answer to the question of "How does the system recognize" is in the programming of the fire alarm system. That's at least for the "Fire Alarm", "Supervisory Alarm", and "Monitor Activations". Troubles are hard-wired into the system; programming won't change anything about displaying a trouble.

Fire Alarm - Supervisory Alarm - Monitor Activation

A fire alarm system doesn't really decide anything; a fire alarm system is told what to do through the program that is implanted into the system.

A fire alarm panel's programming for fire, supervisory, and monitor is divided into two different areas. The first area is the zone or device inputs/outputs and the second area is the control mapping, or rules, of what is done with signals from the zone or device inputs/outputs.

When the Fire Detection and Alarm System (FDAS) is first set up, and also when changes are made to the system, some systems, like EST, have the fire alarms, supervisory alarms, and monitor activations programmed into the zone inputs/outputs and the addressable devices.

Other Fire Detection and Alarm Systems like Silent Knight have all this information programmed into the Fire Alarm Control Panel (FACP) itself.

The fire alarms, supervisory alarms, and monitor activations from the inputs/outputs are next received by the control mapping or control rules in the FACP's programming.

When a Fire Alarm is received by the control part of the FACP's programming, the control panel turns on a red light. Through programming, the internal control mapping or rules turns on the devices to get everyone's attention in the building; in essence telling everyone to get out. The mapping or rules might also call the monitoring company, release the fire doors, shut down air handlers, close smoke dampers, etc. When it comes to actions, fire alarms have the highest priority.

When a Supervisory Alarm is received by the control part of the FACP's programming, the control panel turns on an amber light and local buzzer. A supervisory alarm is still an alarm, just not as noisy as a fire alarm; it won't tell the people in the building to get out. The supervisory alarm mapping or rules might also initiate other actions. When it comes to actions, supervisory alarms have the second highest priority.

Most Fire Alarm Systems (FAS) don't even have the Monitor Activations. Those fire alarm systems that do have monitor activations can turn on an amber light and can turn on a local buzzer. The monitor activations, through programming, can also turn on or off many devices. When it comes to actions, monitor activations have the lowest priority.


Troubles are different. The panel doesn't "decide" whether or not to show a trouble, if there's a trouble, the panel will show it by turning on an amber trouble light and the local buzzer.

A trouble is caused by anything that isn't working right with the fire alarm system itself. Troubles could be coming from the panel, the Signaling Line Circuit (SLC), any addressable devices and modules, and any conventional circuits that connect to the panel or addressable modules. Even when the utility power quits, a trouble will show up on the panel.

All fire alarm panels will show troubles when something isn't working right. Troubles are hard-wired into the fire alarm panel. When it comes to actions, troubles are a lower priority than supervisory alarms, but higher priority than monitor activations.

Douglas Krantz

Mr. Krantz

I need to understand why a trouble signal has a lower priority than a supervisory signal.

Thank you, FT

The word "Priority" is used for "When two messages come in at the same time, which one should the panel handle first?" In small fire alarm systems, priorities don't mean much; in large fire alarm systems, priorities are quite important.

Priorities of the Fire Alarm System

Alarm Priority: The purpose of a fire alarm system is to detect fires, and, if there's a fire, warn people of fires. That's a highest-level priority signal; when there's a fire, no one cares if a wire is broken. Even when a supervisory signal is there, like a valve is closed, it's still more important to get people out of the building than the look for a closed valve. Once the fire alarm is properly sounding off, then the alarm system can look at other, lower-priority type signals.

Supervisory Priority: Secondary to a fire alarm, the fire alarm system is watching other systems connected to the fire alarm system, like the sprinkler system. In other words, the fire alarm system supervises other systems. When a valve on the sprinkler system is closed, people aren't warned of fire, but someone should be told to open the valve again. Once the panel has turned on the panel's local buzzer and the supervisory light, then the panel can look at other, lower-priority type signals.

Trouble Priority: Yes, it's important to make sure the fire alarm system itself is properly working. Once the alarms are sounding (highest priority), and the supervisories are displayed on the panel, then the panel can deal with the trouble signals, like broken wires or dirty smoke detectors. After the panel has looked at the alarms, the supervisories, and the troubles, the panel can take care of the lowest-priority signals.

Monitor Priority: Most fire alarm panels don't have a monitor priority. If the panel does have a monitor priority, the monitor signals are used for things like turning on or off non-emergency equipment. EST is one of the few manufacturers that seem to even have the low-priority monitor signals.

Do Priorities Matter?

On smaller fire alarm systems, ones that have a few dozen detectors and horns, the panel will take care of all fire alarms, supervisory alarms, trouble activations, and monitor signals in a fraction of a second. Because there are so few devices, priorities really don't make a big difference when the systems are small.

On larger systems, systems that have thousands of detectors, cover several buildings, use any one of hundreds of voice announcements, have many hundreds of horns and strobes, and are there are dozens of fire zones, priorities are very important.

Code Blue Alarms in hospitals, for instance, have to be at the full fire alarm priority level. Code Blue Alarms are where a person has quit breathing, and a "Crash Cart" along with trained medical personnel have to arrive within 3 minutes, or the person is dead.

If in a large fire alarm system, the Code Blue Alarm is sent as a supervisory level alarm, the Code Blue announcements can easily take 20 seconds to get through the system and heard by medical personnel. If, however, in the same large fire alarm system the Code Blue Alarm is sent as a fire alarm signal, the Code Blue announcement might take less than a second to get through the system. Twenty seconds may mean the difference between life and death to someone.

Priorities Do Matter

With the speed of signal processing in smaller systems, priorities usually don't matter. However, the larger and more complicated systems with lots of devices and actions need to have different levels of priorities so that the panel can process the Fire Alarms, Supervisory Alarms, Trouble Activations, and Monitor Activations in order of importance.

Douglas Krantz
Life Safety
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