NC Fire Alarm key terms

The wiring path connecting automatic detectors and manual stations to the control unit, supervised for opens, shorts, and ground faults so a single fault is annunciated rather than hidden.

The supervised output circuit that powers horns, strobes, speakers, and other signal devices, sized so voltage at the end of the line stays within the appliance's listed operating range.

A signaling circuit that leaves the control unit and returns on a separate conductor, so an open or ground fault leaves all devices operational and the fault is annunciated.

A two-wire signaling circuit that does not return to the control unit; an open fault disables every device beyond the break, though the fault itself is still annunciated.

A pathway that survives a single open, short, or ground fault and continues to operate all connected devices, typically achieved with redundant paths and isolation modules.

The older NFPA 72 lettering (Style B, D, Y, Z and similar) that maps to Class A or B performance; plans and older specifications often use these letters instead of Class.

A detector, module, or appliance with a unique digital address that lets the panel report the exact device in alarm or trouble rather than only the circuit.

A grouping of non-addressable devices sharing one circuit, so the panel reports only the zone identity, and the technician must search the zone to find the actuated device.

The listed coverage rule, commonly 30 feet (9.1 m) between detectors on smooth ceilings, adjusted for ceiling height, beams, and air movement per the manufacturer's published spacing.

A detector that samples air at one location, using ionization, photoelectric, or combination sensing, and is listed for a defined coverage area rather than for projected-beam sampling.

A smoke detector that projects a light beam across a space to a receiver and responds to obscuration along the path, used for large open areas such as atriums and warehouses.

A detector mounted on or in an HVAC duct that samples moving air to shut down the air handler and, where required, trigger alarm, with its sampling tubes oriented to airflow.

A device that responds to fixed temperature, rate of temperature rise, or both, and is generally used where smoke detection would be unreliable or produce nuisance alarms.

A manually operated initiating device mounted at a listed height on an exit path, with a visible operating mechanism and reset requiring a key or tool.

A device on a sprinkler system that signals sustained water movement indicating a flowing head, with a delay to avoid false alarms from pressure surges.

A supervisory device that reports when a control valve on a suppression system is moved from its normal open or closed position, alerting occupants and staff to impaired protection.

An indication that a system or suppression component is off-normal, such as a closed valve or low pressure, distinct from an alarm and usually annunciated differently.

An audible and visual indication that a circuit, power source, or component has failed or is impaired, requiring acknowledgement and often resounding after a set period.

Silence stops the notification appliances while keeping the alarm condition latched; reset clears the panel, but a still-present alarm condition will re-initiate the sequence.

A panel feature that delays alarm annunciation briefly to confirm a detector signal is sustained, reducing nuisance alarms from transient smoke or dust.

A programmed sequence allowing trained staff a limited window to investigate a detector signal and acknowledge it before general alarm, with automatic alarm if not acknowledged.

The battery or other standby source that keeps the system operational for a defined period when normal power fails, sized for standby plus alarm load and recharge.

The sizing method that adds standby current times standby hours to alarm current times alarm minutes, applies a derating factor, and adds recharge capacity to select battery amp-hours.

The method of summing conductor resistance over the circuit length and multiplying by load current to confirm appliances at the end of a NAC still receive their minimum listed voltage.

The requirement that strobes and other visual appliances flash together within a defined time window when on the same circuit or in the same view, to limit photosensitive seizure risk.

The measure of a strobe's light output; higher candela is required in larger rooms and corridors, and the rating must match the listing for the installed location.

A horn, speaker, or sounder that produces the alarm signal, with sound pressure level set above ambient noise and measured at the required distance from the pillow.

A notification system using amplified speakers and prerecorded or live messages to direct occupants, with intelligibility requirements so speech is understandable in the occupied space.

A periodic check that a smoke detector responds within its listed obscuration range, using a calibrated test instrument rather than smoke or a magnet.

The scheduled program of visual inspection, functional testing, and maintenance that keeps a system reliable, documented on forms retained for the code-required period.

The document the installer prepares and delivers at handover, recording system features, device locations, and owner responsibilities for testing and maintenance.

A facility that receives and acts on signals from a protected premises, such as a central station, proprietary station, or remote receiving point.

A drawing revised during installation to show the system as actually constructed, including device locations, circuit routing, and any field changes from the permit set.

A single-line schematic showing how panels, circuits, and devices interconnect vertically and functionally, used to trace pathways during design, review, and troubleshooting.

The space between ceiling beams deep enough to affect smoke spread, requiring detectors in each pocket or a spacing adjustment based on the beam depth and ceiling area.

The reduction in listed spacing applied for high ceilings, joists, or other obstructions so smoke reaches a detector before it stratifies or is diluted.

The state law and administrative rules that define licensure, scope of work, supervision, continuing education, and grounds for discipline for alarm contractors.

The individual who passes the required examination and holds the license for a contracting business, carrying responsibility for code compliance and supervision of work.

Proof of general liability and, where required, workers' compensation coverage that a contractor must maintain and often file with the licensing board or permitting authority.

The method of summing conductor resistance over the circuit length and multiplying by load current to confirm appliances at the end of a NAC still receive their minimum listed voltage.