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Fire Protection Glossary - C


Cabinet. Fire alarm control unit enclosure.

CABO. Council of American Building Officials, 5203 Leesburg Pike, Falls Church, VA 22041.

Carrier. High frequency energy that can be modulated by voice or signaling impulses.

Carrier System. A means of conveying a number of channels over a single path by modulating each channel on a different carrier frequency and demodulating at the receiving point to restore the signals to their original form.

Cathode Ray Tube (CRT). An electronic tube used to display data, such as a monitor, that is coated internally with a phosphorescent material. When the electron beam strikes the phosphor, an electron is in turn released thus causing it to glow.

Ceiling. The upper surface of a space, regardless of height. Areas with a suspended ceiling have two ceilings, one visible from the floor and one above the suspended ceiling.

Ceiling Height. The height from the continuous floor of a room to the continuous ceiling of a room or space.

Ceiling Surfaces. Ceiling surfaces referred to in conjunction with the locations of initiating devices are defined as follows:

Beam Construction. Ceilings having solid structural or solid nonstructural members projecting down from the ceiling surface more than 4 in. (100 mm) and spaced more than 3 ft (0.9 m) center to center.

Girder. A support for beams or joists that runs at right angles to the beams or joists. Where the top of girders are within 4 in. (100 mm) of the ceiling, they are a factor in determining the number of detectors and are to be considered as beams. Where the top of the girder is more than 4 in. (100 mm) from the ceiling, it is not a factor in detector locations.

Central Processing Unit (CPU). An arrangement of circuitry using computer circuit techniques usually consisting of memory elements, signal processing circuitry, and a means to input and output data at very high speed.

Central Station. A supervising station that is listed for central station service.

Central Station Fire Alarm System. A system or group of systems in which the operations of circuits and devices are transmitted automatically to, recorded in, maintained by, and supervised from a listed central station having competent and experienced servers and operators who, upon receipt of a signal, take such action as required by this code. Such service is to be controlled and operated by a person, firm, or corporation whose business is the furnishing, maintaining, or monitoring of supervised fire alarm systems.

Central Station Service. The use of a system or a group of systems in which the operations of circuits and devices at a protected property are signaled to, recorded in, and supervised from a listed central station having competent and experienced operators who, upon receipt of a signal, take such action as required by NFPA 72, National Fire Alarm ode. Related activities at the protected property such as equipment installation, inspection, testing, maintenance, and runner service are the responsibility of the central station or a listed fire alarm service-local company. Central station service is controlled and operated by a person, firm, or corporation whose business is the furnishing of such contracted services or whose properties are the protected premises.

Certification. A systematic program using randomly selected follow-up inspections of the certified systems installed under the program that allows the listing organization to verify that a fire alarm system complies with all the requirements of this code. A system installed under such a program is identified by the issuance of a certificate and is designated as a certificated system.

Certification of Personnel. A formal program of related instruction and testing as provided by a recognized organization or the authority having jurisdiction.

Channel. A path for voice or signal transmission utilizing modulation of light or alternating current within a frequency band.

Chime. A single-stroke or vibrating-type audible signal appliance that has a xylophone-type striking bar.

Circuit. The conductors or radio channel and associated equipment used to perform a definite function in connection with an alarm system.

Circuit Interface. A circuit component that interfaces initiating devices or control circuits, or both, notification appliances or circuits, or both, system control outputs, and other signaling line circuits to a signaling line circuit.

Circuit Resistance. The total resistance measured at the termination point of a circuit, excluding any connected components.

Class A Circuit. Circuits capable of transmitting an alarm signal during a single open or a nonsimultaneous single ground fault on a circuit conductor shall be designated as Class A. It is commonly known as a 4-wire circuit.

Class B Circuit. Circuits not capable of transmitting an alarm beyond the location of a single open or a nonsimultaneous single ground fault on a circuit conductor shall be designated, as Class B. It is commonly known as a 2-wire circuit with end-of-line resistor.

Cloud Chamber Smoke Detection. The principle of using an air sample drawn from the protected area into a high humidity chamber combined with a lowering of chamber pressure to create an environment in which the resultant moisture in the air condenses on any smoke particles present, forming a cloud, The cloud density is measured by a photoelectric principle. The density signal is processed and used to convey an alarm condition when it meets preset criteria.

Coded. An audible or visible signal conveying several discrete bits or units of information. Notification signal examples are numbered strokes of an impact-type appliance and numbered flashes of a visible appliance.

Coded Signal. A signal pulsed in a prescribed code for each round of transmission. A minimum of three rounds and a minimum of three impulses are required for an alarm signal.

Combination Detector. A device that either responds to more than one of the fire phenomenon or employs more than one operating principle to sense one of these phenomenon. Typical examples are a combination of a heat detector with a smoke detector or a combination rate-of-rise and fixed-temperature heat detector.

Combination Fire Alarm and Guard's Tour Box. A manually operated box for separately transmitting a fire alarm signal and a distinctive guard patrol tour supervisory signal.

Combination System. A fire alarm system whose components might be used, in whole or in part, in common with a nonfire signaling system, such as a paging system, a security system, a building automatic system, or a process monitoring system.

Combustible. Capable of undergoing combustion.

Combustion. A chemical process that involves oxidation sufficient to produce light or heat.

Communications Channel. A circuit or path connecting a subsidiary station(s) over which signals are carried.

Compatibility Listed. A specific listing process that applies only to two-wire devices (such as smoke detectors) designed to operate with certain control equipment.

Compatible (Equipment). Equipment that interfaces mechanically or electrically as manufactured without field modification.

Contiguous Property. A single-owner or single-user protected premises on a continuous plot of ground, including any buildings thereon, that is not separated by a public thoroughfare, transportation right-of-way, property owned or used by others, or body of water not under the same ownership.

Control-by-Event. A method of providing a variety of output responses based upon various initiating conditions (events).

Control Unit. A system component that monitors inputs and controls outputs through various types of circuits.

Conventional Control Panel. A fire alarm panel that can only monitor on/off signals.

Cross-Zone. An initiating circuit configuration, which allows an alarm only after two or more devices, is in alarm.

Critical Radiant Flux. The level of incident radiant heat energy on a floor covering system at the most distant flameout point as determined by the test procedure of NFPA 253, Standard Method of Test for Critical Radiant Flux of Floor Covering Systems Using a Radiant Heat Energy Source. The unit of measurement of critical radiant flux is watts per square centimeter (W/sq. cm).
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by Michael B. Baker. All rights reserved.
ISSN 1554-074X

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Some information may be found within this web site that is reprinted with permission from one or more of the following: NFPA 70 National Electrical Code®,NFPA 72® National Fire Alarm Code®, & NFPA 101® Life Safety Code®, Copyright© NFPA, Quincy, MA 02269.

This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety.