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Fire Protection Glossary - P-Q


P - Q


Paging System. A system intended to page one or more persons by such means as voice over loudspeaker, coded audible signals, or lamp annunciators.

Parallel Telephone System. A telephone system in which an individually wired circuit is used for each fire alarm box.

Parallel Telephone Auxiliary Alarm System. See Auxiliary Fire Alarm System.

Particles of Combustion. Substances resulting from the chemical process of fire. Such particles include ash wish remains at the site of the fire and volatile products, which may evaporate, agglomerate, or condense.

Path (Pathways). Any conductor, optic fiber, radio carrier, or other means for transmitting fire alarm system information between two or more locations.

Permanent Visual Record (Recording). An immediately readable, not easily alterable, print, slash, or punch record of all occurrence of status changes.

Photoelectric Light Obscuration Smoke Detection. The principle of utilizing a light source and a photosensitive sensor onto which the principal portion of the source emissions is focused. When smoke particles enter the light path, some of the light is scattered and some is absorbed, thereby reducing the light reaching the receiving sensor. The light reduction signal is processed and used to convey an alarm condition when it meets preset criteria. The response of photoelectric light obscuration smoke detectors is usually not affected by the color of smoke. Smoke detectors utilizing the light obscuration principle are usually of the line type. These detectors are commonly refereed to as "projected beam smoke detectors."

Photoelectric Light-Scattering Smoke Detection. The principle of utilizing a light source and a photosensitive sensor arranged in a manner so that the rays from the light source do not normally fall onto the photosensitive sensor. When smoke particles enter the light path, some of the light is scattered by reflection and refraction onto the sensor. The light signal is processed and used to convey an alarm condition when it meets preset criteria. Photoelectric light-scattering smoke detection is more responsive to visible particles (larger than 1 micron in size) produced by most smoldering fires. It is somewhat less responsive to the smaller particles typical of most flaming fires.

Plant. One or more buildings under the same ownership or control on a single property.

Plenum. An air compartment or chamber to which one or more ducts are connected and that forms part of an air distribution system.
NOTE: The definition of plenum is not intended to apply to the space above a suspended ceiling that is used for environmental air referred to in NFPA 70-2002 300.22(C).

Positive Alarm Sequence. An automatic sequence that results in an alarm signal even when manually delayed for investigation, unless the system is reset.

Positive Non-Interfering (PNI) System. A system in which the alarm initiating devices are electrically arranged such that if one device is operated to transmit an alarm, no other devices connected to the same circuit is allowed to interfere with the transmission of a complete and unmodified round of alarm signals.
Positive Non-Interfering and Successive System. A system which prevents subsequently operated initiating devices from interfering with the transmission of an alarm from an operated device and which permits any device to transmit, in turn, its assigned number of rounds of coded signals once the previously actuated device completes its transmission of coded signals.

Power Limited Circuit. A circuit that limits power to the load inherently or by overcurrent protection.

Power Supply. A source of electrical operating power including the circuits and terminations connecting it to the dependent system components.

Presignal System. A feature that allows initial fire alarm signals to sound only in department offices, control rooms, fire brigade stations, or other constantly attended central locations and for which human action is subsequently required to activate a general alarm, or a feature that allows the control equipment to delay the general alarm by more than 1 minute after the start of the alarm processing.

Primary Battery (Dry Cell). A nonrechargeable battery requiring periodic replacement.

Primary Trunk Facility. That part of a transmission channel connecting all leg facilities to a supervising or subsidiary station.

Prime Contractor. The one company contractually responsible for providing central station services to a subscriber as required by this code. This can be either a listed central station or a listed fire alarm service-local company.

Private Radio Signaling. A radio system under control of the proprietary supervising station.

Projected Beam-Type Detector. A type of photoelectric light obscuration smoke detector wherein the beam spans the protected area.

Proprietary Supervising Station. A location to which alarm or supervisory signaling devices on proprietary fire alarm systems are connected and where personnel are in attendance at all times to supervise operation and investigate signals.

Proprietary Supervising Station Fire Alarm System. An installation of fire alarm systems that serves contiguous and noncontiguous properties, under one ownership, from a proprietary supervising station located at the protected property, at which trained, competent personnel are in constant attendance. This includes the proprietary supervising station; power supplies; signal-initiating devices; initiating device circuits; signal notification appliances; equipment for the automatic, permanent visual recording of signals; and equipment for initiating the operation of emergency building control services.

Protected Premises. The physical location protected by a fire alarm system.

Protected Premises (Local) Control Unit (Panel). A control unit that serves the protected premises or a portion of the protected premises and indicated the alarm via notification appliances inside the protected premises.

Protected Premises (Local) Fire Alarm System. A protected premises system that sounds an alarm at the protected premises as the result of the manual operation of a fire alarm box or the operation of protection equipment or system, such as water flowing in a sprinkler system, the discharge of carbon dioxide, the detection of smoke, or the detection of heat.

Public Fire Service Communications Center. The building or portion of the building used to house the central operating part of the fire alarm system; usually the place where the necessary testing, switching, receiving, transmitting, and power supply devices are located.

Public Switched Telephone Network. An assembly of communications facilities and central office equipment operated by authorized common carriers that provides the general public with the ability to establish communications channels via discrete dialing codes.
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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.