Fire Alarm Control Panel

240px-Potomac_hall_facpfire alarm control panel (FACP), or fire alarm control unit (FACU), is an electric panel that is the controlling component of a fire alarm system. The panel receives information from environmental sensors designed to detect changes associated with fire, monitors their operational integrity and provides for automatic control of equipment, and transmission of information necessary to prepare the facility for fire based on a predetermined sequence. The panel may also supply electrical energy to operate any associated sensor, control, transmitter, or relay. There are four basic types of panels: coded panels, conventional panels, addressable panels, and multiplex systems. A fire alarm control panel is required under the building code for a majority of new commercial building construction in most countries.

Coded panels

250px-Simplex4247Coded panels were the earliest type of central fire alarm control, and were made from the 1940s to the late 1970s. A coded panel is similar in many ways to a modern conventional panel (described below), except each zone was connected to its own code wheel (Ex: An alarm in zone 1 would sound code 1-2-4 [through the bells or horns in the building], while zone 2 would sound 1-2-5), which, depending on the way the panel was set up, would either do sets of four rounds of code until the initiating pull station was reset (similar to a coded pull station) or run continuously until the panel itself was reset. Large panels could take up an entire wall in a mechanical room, with dozens of code wheels. Lists of codes had to be maintained, sometimes with copies being posted above certain pull stations (this setup is commonly seen in older wings of hospitals). Smaller panels could be set up in one of two ways. Most of the time, the panel would only have one zone, and therefore, only one code. Common one-zone codes were 4-4-0 and 17-0-0 (which is similar to the 120 bpm March Time setting found on modern panels). Alternatively, the panel could be made with no code wheels, using only what was called the gong relay. In large systems, this was primarily used to accommodate existing coded pull stations. However, it could also be used as its own zone, with the connected horns or bells sounding continuously instead of in a particular code. Examples of this type of panel include the IBM 4201 and the Simplex 4246. These panels are not very common today, but can sometimes be found in older buildings such as those on college campuses or hospitals.

Conventional panels

200px-Simplex_FACPConventional panels have been around ever since electronics became small enough to make them viable. They are no longer used frequently in large buildings, but are still used on smaller sites such as small schools, stores, restaurants, and apartments.

A conventional system employs one or more initiating circuits, connected to sensors (initiating devices) wired in parallel. These sensors are devised to decrease the circuits resistance when the environmental influence on any sensor exceeds a predetermined threshold. In a conventional system the information density is limited to the number of such circuits used. A small map of the building is often placed near the main entrance with the defined zones drawn up, and LEDs indicating whether a particular circuit/zone has been activated. Another common method is to have the different zones listed in a column, with an LED to the left of each zone name. Examples include the Edwards 6500 and the Simplex 4005 or 4006.

The main drawback with conventional panels is that one cannot tell which device has been activated within a circuit. The fire may be in one small room, but as far as emergency responders can tell, a fire could exist anywhere within a zone. The same applies to coded panels, which nowadays are no longer made, but can be found in old systems. These, if the decision is made to keep them, are “grandfathered” in under NFPA regulations.


Multiplex systems

200px-Simplex21204100Multiplex systems, a sort of transition between conventional and modern addressable systems, were often used in large buildings and complexes from the mid to late 1970s into the late 1980s. Early on, these systems were programmed to function as large conventional systems. Gradually, later installations began to feature components and features of modern addressable systems. These systems were often capable of controlling more than a building’s fire alarm system (i.e. HVAC, security, electronic door locks…) without any type of alarm or trouble condition present. An example of this type of system is the Simplex 2120. While the main panel was the brains of the system and could be used to access certain functions, fire alarm controls were usually accessed through transponders. These were smaller conventional panels programmed to ‘communicate’ the status of part of the system to the main panel and also could be used to access basic fire alarm control functions. The original Simplex 4100 was meant to be used this way.

Addressable panels

200px-Simplex4100UAddressable panels are usually much more advanced than their conventional counterparts, with a higher degree of programming flexibility and single point detection. Addressable fire alarm panels were introduced by many manufacturers during the microcontroller boom in the mid 1980s. Examples include the Simplex 4100U and the Notifier Onyx.

Signaling line circuit loops

Panels usually have a number of signaling line circuit loops – usually referred to as loops or SLC loops – ranging between one and thirty. Depending on the protocol used, a loop can monitor and control several hundred devices. Some protocols permit any mix of detectors and input/output modules, while other protocols have 50% of channel capacity restricted to detectors/sensors and 1/2 restricted to input/output modules. Each SLC polls the devices connected, which can number from a few devices to several hundred, depending on the manufacturer. Large systems may have multiple SLCs, and SLCs are further divided into sub-groups through the use of fault-isolation modules.

Each device on a SLC has its own address, and so the panel knows the state of each individual device connected to it. Common addressable input (initiating) devices include

Addressable output devices are known as relays and include

  • (Warning System/Bell) Relays
  • Door Holder Relays
  • Auxiliary (Control Function) Relays

Relays are used to control a variety of functions such as

  • Switching fans on or off
  • Closing/opening doors
  • Activating fire suppression systems
  • Activating notification appliances
  • Shutting down industrial equipment
  • Activating another fire alarm panel


Also known as “cause and effect” or “programming”, mapping is the process of activating outputs depending on which inputs have been activated. Traditionally, when an input device is activated, a certain output device (or relay) is activated. As time has progressed, more and more advanced techniques have become available, often with large variations in style between different companies.


Zones are usually made by dividing a building, or area into different sections, and placing each device in the building in a different zone.


Groups contain multiple output devices such as relays. This allows a single input, such as a smoke detector or MCP, to have only one output programmed to a group, which then maps to between two to many outputs or relays. This enables an installer to simplify programming by having many inputs map to the same outputs, and be able to change them all at once, and also allows mapping to more outputs than the programming space for a single detector/input allows.

Boolean logic

This is the part of a fire panel that has the largest variation between different panels. It allows a panel to be programmed to implement fairly complex inputs. For instance, a panel could be programmed to notify the fire department only if more than one device has activated. It can also be used for staged evacuation procedures in conjunction with timers.


The principle of networking involves connecting several panels together to form a system. Inputs on one panel may activate outputs on another, for example, or the network may allow monitoring of many systems. Networking is often used in situations where one panel is not large enough, or in multiple-building situations.

Although quasi-standards exist that allow panels from different manufacturers to be networked with each other, they are not in favor with a lot of companies. One of the most common protocols used BACnet which is used for various type of industrial networks.

More recently, some panels are being networked with standard Ethernet, but this is not yet very common. Most organizations choose to create their own proprietary protocol, which has the added benefit of allowing them to do anything they like, allowing the technology to progress further. However, a bridging layer between the proprietary network and BACnet is usually available.

Networking may be used to allow a number of different panels to be monitored by one graphical monitoring system.


In nearly every state in the USA, the International Building Code requires fire alarm and sprinkler systems to be monitored by an approved supervising station.

A fire alarm system consists of a computer-based control connected to a central station. The majority of fire alarm systems installed in the USA are monitored by a UL listed or FM Global approved supervising station.

These systems will generally have a top level map of the entire site, with various building levels displayed. The user (most likely a security guard) can progress through the different stages. From top level site → building plan → floor plan → zone plan, or however else the building’ssecurity system is organised.

A lot of these systems have touch screens, but most users tend to prefer a mouse (and a normal monitor), as it is quite easy for a touch screen to become misaligned and for mistakes to be made. With the advent of the optical mouse, this is now a very viable option.

System functions

180px-Fire_alarm_panel_resetThere are many functions on a fire alarm panel. Some of these are:

System reset

This resets the panel after an alarm condition. All initiating devices are reset, and the panel is cleared of any alarm conditions. If an initiating device is still in alarm after the system is reset, such as a smoke detector continuing to sense smoke, or a manual pull station still in an activated position, another alarm will be initiated. A system reset is often required to clear supervisory conditions. A system reset does not usually clear trouble conditions. Most trouble conditions will clear automatically when conditions are returned to normal.

On UK panels a “Silence” or “Acknowledge” is usually required before a “System Reset” can be performed.


This function, also abbreviated to “ACK”, is used to acknowledge an abnormal situation such as an alarm, trouble or supervisory. The acknowledge function tells the panel that building personnel or emergency responders are aware of the alarm, trouble, or supervisory condition. Acknowledging the alarm or trouble condition also normally silences the panel’s own sounder, but does not silence any alarms.


Also known as “manual evacuation” or “evacuate”. On panels that have this function, the drill function activates the system’s notification appliances, often for purposes of conducting a fire drill. Using the drill function, an alarm is normally not transmitted to the fire department or monitoring center. However, building personnel often notify these agencies in advance in case an alarm is inadvertently transmitted.

Walk test

Will allow the functional testing of the systems initiation and notification devices without the assistance of additional people at the control panel itself.

On UK panels this is usually an engineer-only function and cannot be activated by a user.

Signal silence

Also known as “alarm silence” or “audible silence”. Depending on the configuration of the alarm system, this function will either silence the system’s notification appliances completely, or will silence only the audible alarm, with strobe lights continuing to flash. Audible silence allows for easier communication amongst emergency responders while responding to an alarm. This can also be used during construction as a means of a preliminary test, before the final full test.

Lamp test

Also known as “flash test”. This button is known to have become obsolete, but is still used on many panels. This function is used to check the condition of the LEDs themselves. A “Lamp Test” button is required by code on multi-zone panels installed in Canada. Many panels do a lamp test when the system is reset.

Alarm circuit supervision

Various forms of alarm circuit supervision have been used to indicate trouble with an alarm circuit. Possible alarm circuit faults on a two wire circuit include one of the conductors being shorted to ground, open circuit (conductor continuity break), or a short circuit between the conductors. Also the circuits could be tampered with by having an external AC or DC voltage applied with various duty cycles or waveforms. There are a number of US patents that address this issue and some have been implemented in available system products. One of the first to address this issue was Patent No. 3,588,890 “Resistance Sensing Supervisory System” issued on June 28th 1971 and assigned to General Motors Corporation. General Motors used this supervision on all circuits installed in GM plants starting in 1970. An improvement to this basic “Resistance Sensing Supervisory System” can be obtained by providing a pulsed or time dependent variable voltage applied to the alarm circuit and is addressed in US patent numbers 4,030,095 and 4,716,401.

Panel alerting

Many panels today have the capability of alerting building personnel of a situation which can arise into a potentially serious problem. Fire alarm panels indicate an abnormal condition is via a solid or flashing LED. Some panels also contain a small sounder, used in conjunction with the visual alert. A number of indicators are shown below. Note that not all fire alarm panels have all of these indicators.


Also known as “Fire”. This indicator is lit when an alarm condition exists in the system, initiated by smoke detectorsheat detectors, sprinkler flow switches, manual pull stationsmanual call points, or otherwise. Along with the indicator on the panel, notification appliances, such as horns and strobes, are also activated, signaling a need to evacuate to building occupants. In an alarm condition, the fire alarm panel indicates where the alarm originated. The alarm panel can be reset once the device which initiated the alarm is reset, such as returning the handle of a manual pull station to its normal position.

Audible silence

The Audible Silence indicator is used in conjunction with the “Alarm” indicator. It indicates that the fire alarm panel is still in an alarm condition, but that notification appliances have been silenced. While the alarm is silenced, other functions in an alarm condition continue to operate, such as emergency service for elevators, stairway pressurization, and ventilation functions. A new alarm initiation while the alarm is silenced will take the panel out of Audible Silence and reactivate the notification appliances.

Brigade called

This indicator is activated when emergency responders have been automatically notified by the fire alarm system. Requirements vary depending on jurisdiction regarding whether a direct connection to the fire department is required, optional, or prohibited. If a connection to the fire department is optional, or is prohibited, a fire alarm system is often connected to a monitoring center at the building owner’s discretion.


On panels containing this function, the “Drill” indicator shows that the alarm condition was activated from the fire alarm panel, often in order to conduct a fire drill. When an alarm is initiated for a drill, the fire department or monitoring company is usually not notified automatically. However, building personnel preparing to conduct a fire drill often will provide advance notice of a drill to the fire department and monitoring center in case an alarm is unintentionally transmitted.


Also known as “Defect”. When held steady or flashing, it means that a trouble condition exists on the panel. Trouble conditions are often activated by a contaminated smoke detector or an electrical problem within the system. Trouble conditions are also activated by a zone being disabled (disconnected from the system), a circuit being disabled, low power on the backup battery, the disabling of a notification appliance, the ground faults, or short or open circuits. Usually the alarm panel’s sounder will activate if a trouble condition exists, though older systems would sometimes activate a bell or other audible signal connected to the panel. In a trouble condition, the panel displays the zone or devices causing the condition. The “Trouble” indicator goes out automatically when the situation causing the trouble condition is rectified and some panels have more specific indicators such as ‘Trouble-PSU’ which shows when the panel itself is compromised and ‘Trouble-Bell’ (‘Sounder fault’ on UK panels) which shows that the sounders are not functioning correctly.


This signal indicates that a portion of the building’s fire protection system has been disabled (such as a fire sprinkler control valve being closed and, consequentially, a sprinkler tamper switch being activated), or, less frequently, that a lower priority initiating device has been triggered (such as a duct smoke detector). The “Supervisory” indicator may go out automatically when the condition has cleared, but usually requires a “Reset” to clear.

AC power

Also known as “Normal”. When this indicator is lit, power is being provided to the system from the building’s electrical system, and not from the backup battery. When an AC power condition changes, the Trouble indicator comes on and the AC power indicator goes off and the screen alerts building personnel of a power failure. If the AC power indicator is lit without any other indicators also lit, then the system is in a normal condition. If no LEDs are lit, there is no power source feeding the panel.

DC power

This is used to tell the operator that DC power (batteries) are being charged or used. While using DC power, the system remains in a trouble condition.


This LED is on when there are unusual power-line conditions.

Priority 2 alarm/security

This LED is common on top-of-the-line intelligent panels. This LED can only activate if there is a secondary device hooked into the “Priority 2 Alarm/Security” terminals. This secondary device could be a security system, building management system, or another fire alarm control panel. Depending on how the panel is programmed, the panel’s alarms may or may not activate when a condition like this is present.


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