to transmit a signal even with an open or ground fault on the circuit while
Class B circuits need not. The loop connection can be “fault-tolerant” thus
allowing continual operation if there is a break in the cable or a device failure.
The connection of the FACP to the devices can be “addressable” or “super-
vised.” Before devices were addressable an alphanumeric display at the control
panel indicated which zone was affected. Addressable means that the FACP
can communicate to a single device or a group of devices depending on the
functions required and know the exact location of the device. Supervised
devices are monitored to ensure that they are still connected to the FACP
and are operational.
Regardless of whether devices are supervised or addressable the system is
required to continuously monitor their status. For addressable devices moni-
toring is accomplished by polling individual devices. For nonaddressable
devices monitoring is accomplished by sensing electric current. The FACP pro-
vides a small current which, if interrupted, indicates trouble such as a failed or
missing device.
A control panel is fed by standard branch-circuit wiring and typically
includes alphanumeric display and touchpad to provide information on the
state of the system. This allows a technician to shun an alarm or reprogram
or reset the systems. The panel may include batteries to provide power for
its operation if AC power fails.
Annunciator Panel
A major component to the system is the annunciator panel attached to the
FACP. The annunciator provides visual and audible indications that an alarm
has been initiated as well as the location of the alarm. It may also identify the
functions that could affect the fire and the building occupants in the area.
A basic annunciator panel may have an alphanumeric display, and switches
to acknowledge and silence the alarm. More sophisticated annunciator panels
are equipped with a monitor or include a personal computer with a GUI
displaying floor plans of the building and the location of the alarm.
Fire Detection
Fire consists of smoke, heat, and light. The system components that detect the
fire and initiate an alarm monitor one or more of the fire’s characteristics. The
detection components of a fire alarm system are typically located in ceilings,
HVAC ducts, mechanical and electrical areas and equipment rooms.
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