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A Fire Alarm System is an active fire protection system that detects fire or the
effects of fire, and as a result provides one or more of the following: notifies
the occupants, notifies persons in the surrounding area, summons the fire service,
and controls all the fire alarm components in a building. Fire alarm systems can
include alarm initiating devices, alarm notification appliances, control units,
fire safety control devices, annunciators, power supplies, and wiring.
Fundamental Design A fire alarm system is
composed of components which can be classified into the following categories.
Initiating Devices - these devices either sense the effects of a fire, or are manually
activated by personnel, resulting in a signal to the fire alarm panel. Examples
are heat detectors, smoke detectors, manual pull stations or call points, and sprinkler
pressure or flow switches.
Main Fire alarm control (panel) - this is the central brain of the overall system,
which coordinates the signals and resultant actions of the system.
Fire Alarm Control Unit (Panel) - any panel providing required functions, and has
inputs and outputs. NAC Power booster panels are the most common example.
Power supply - because one of the fire alarm system objectives is life safety, fire
alarm system power supplies are redundant, and reliable when compared to electronic
or electrical systems of similar complexities (e.g., HVAC control systems). Primary
supply- Commercial light and power. Back-up/secondary supply - Usually sealed, lead-acid
batteries. NAC power supplies for additional notification appliances beyond the
original capability of the FACP. Generators are permitted under strict rules.
Notification appliances - these devices provide stimuli for initiating emergency
action and provide information to users, emergency response personnel, and occupants.
Examples are bell, siren, horn, speaker, light, or text display that provides audible,
tactile, or visible outputs.
Signaling line circuits (SLC)- the wiring which carries data information.
Supervisory signals - detecting devices and signaling to indicate a condition in
fire protection systems which is not normal and could prevent the fire protection
system from functioning as intended in the event of a fire. An example is a closed
valve which controls the water supply to a fire sprinkler system. This does not
indicate the failure of a component or subsystem of the fire alarm system.
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