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Fire Protection Glossary - R


Radiant Energy Sensing Fire Detector. See Automatic Fire Detector.

Radio Alarm Central Station Receiver (RARSR). A system component that receives radio signals. This component resides at a repeater station that is located at a remote receiving location.

Radio Alarm Supervising Station Receiver (RASSR). A system component that receives data and annunciates that data at the supervising station.

Radio Alarm System (RAS). A system in which signals are transmitted from a radio alarm transmitter (RAT) located at a protected premises through a radio channel to two or more radio alarm repeater station receivers (RARRSR) and are annunciated by a radio alarm supervising station receiver (RASSR) located at the central station.

Radio Alarm Transmitter (RAT). A system component at the protected premises to which initiating devices or groups of devices are connected. The RAT transmits signals indicating a status change of the initiating devices.

Radio Channel. A band of frequencies of a width sufficient to allow its use for radio communications. The width of the channel depends on the type of transmissions and the tolerance for the frequency of emission. Channels normally are allocated for radio transmission in a specified type for service by a specified transmitter.

Rate Compensation Detector. A device that responds when the temperature of the air surrounding the device reaches a predetermined level, regardless of the rate of temperature rise. A typical example is a spot-type detector with a tubular casing of a metal that tends to expand lengthwise as it is heated and an associated contact mechanism that closes at a certain point in the elongation. A second metallic element inside the tube exerts an opposing force on the contacts, tending to hold them open. The forces are balanced in such a way that, on a slow rate-of-temperature rise, there is more time for heat to penetrate to the inner element, which inhibits contact closure until the total device has been heated to its rated temperature level. However, on a fast rate-of-temperature rise, there is not as much time for heat to penetrate to the inner element, which exerts less of an inhibiting effect so that contact closure is achieved when the total device has been heated to a lower temperature. This, in effect, compensates for thermal lag.

Rate-of-Rise Detector. A device that responds when the temperature rises at a rate exceeding a predetermined value. Typical examples of rate-of-rise detectors follow Pneumatic Rate-of Rise Tubing. A line-type detector comprising small-diameter tubing, usually copper, that is installed on the ceiling or high on the walls throughout the protected area. The tubing is terminated in a detector unit containing diaphragms and associated contacts set to actuate at a predetermined pressure. The system is sealed except for calibrated vents that compensate for normal changes in temperature.

Spot-Type Pneumatic Rate-of-Rise Detector. A device consisting of an air chamber, a diaphragm, contacts, and a compensating vent in a single enclosure. The principle of operation is the same as that described for pneumatic rate-of-rise tubing.

Thermoelectric Effect Detector. A device in which a sensing element comprises a thermocouple or thermopile unit that produces an increase in electric potential in response to an increase in temperature. This potential is monitored by associated control equipment, and an alarm is initiated when the potential increases at an abnormal rate.

Electrical Conductivity-Type Rate-of-Rise Detector. A line-type or spot-type sensing element whose resistance changes due to a change in temperature. The rate of change of resistance is monitored by associated control equipment, and an alarm is initiated when the rate of temperature increase exceeds a preset value.

Record Drawings. Drawings (as-built) that document the location of all devices, appliances, wiring sequences, wiring methods, and connections of the components of the fire alarm system as installed.

Record of Completion. A document that acknowledges the features of installation, operation (performance), service, and equipment with representation by the property owner, system installer, system supplier, service organization, and the authority having jurisdiction.

Rectifier. An electrical device without moving parts that changes alternating current to direct current.

Relocation. The movement of occupants from a fire zone to a safe area within the same building.

Remote Supervising Station Fire Alarm System. A system installed in accordance with this code to transmit alarm, supervisory, and trouble signals from one or more protected premises to a remote location at which appropriate action is taken.

Repeater Facility. Equipment needed to relay signals between supervisory stations, subsidiary stations, and protected premises.

Repeater Station. The location of the equipment needed for a repeater facility.

Reset. A control function that attempts to return a system or device to its normal, nonalarm state.

Residential Occupancy. Residential occupancies are those occupancies in which sleeping accommodations are provided for normal residential purposes and include all buildings designed to provide sleeping accommodations except for those occupancies classified under health care or detention and correctional occupancies. Residential occupancies include hotels, motels, and dormitories; apartment buildings; lodging or rooming houses; one- and two-family dwellings; and board and care facilities.

Restorable Initiating Device. A device in which a sensing element is not ordinarily destroyed in the process of operation. Restoration can be manual or automatic.

Retard (Adjustable) Waterflow Switches. An adjustable time delay mechanism in a waterflow switch located between the paddle-operated stem and the initiating contacts. This type of switch is designed to prevent brief water flow surges due to water hammer and/or pressure variations from causing an unwanted alarm signal.

Reverse Polarity Interface. A connection from a control unit to a supervising station which operates using polarity reversal to signal an alarm, supervisory, or trouble signals.

Ring-Back Circuit. A circuit which function much like a two-way switch. When a trouble condition occurs, a trouble buzzer and light is energized. When an acknowledge button is depressed, the trouble buzzer and light are reset. When the trouble condition is corrected, the buzzer and light once again are energized indicating an off-normal condition. Once the acknowledge button is released, the circuit returns to normal.

Runner. A person other than the required number of operators on duty at central, supervising, or runner stations (or otherwise in contact with these stations) available for prompt dispatching, when necessary, to the protected premises.

Runner Service. The service provided by a runner at the protected premises, including resetting and silencing of all equipment transmitting fire alarm or supervisory signals to an off-premises location.
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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.