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Fire Protection Glossary - S


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Satellite Station. A normally unattended remote location. Interconnection of signal-receiving equipment or communication channels from protected premises, which include circuits connecting central supervising station(s) are accomplished here.

Satellite Trunk. A circuit or path connecting a satellite to its central or proprietary supervising station.

SBCCI. Southern Building Code Congress International, Inc., 900 Montclair Rd, Birmingham, AL 35213.

Scanner. Equipment located at the telephone company wire center that monitors each local leg and relays status changes to the alarm center. Processors and associated equipment might also be included.

Secondary Power. See Standby Battery.

Secondary Trunk Facility. That part of a transmission channel connecting two or more, but fewer than all, leg facilities to a primary trunk facility.

Separate Sleeping Area. An area of the family living unit in which the bedrooms (or sleeping rooms) are located. Bedrooms (or sleeping rooms) separated by other use areas, such as kitchens or living rooms (but not bathrooms) are considered as separate sleeping areas.

Shall. Indicates a mandatory requirement.

Shunt Non-Interfering (SNI) Coded System. A coded system in which a fire alarm station, once actuated, transmits not less than three rounds of coded alarm signals without interference from any station electrically more distant from the control unit.

Shunt Non-Interfering Successive (SNIS) Coded System. A shunt non-interfering system in which a fire alarm station, when interrupted by a station electrically closer to the control panel, will complete the sending of the interrupted portion of its code when the station with higher priority completes transmission.

Shapes of Ceilings. The shapes of ceilings are classified as follows:

Sloping Ceiling. A ceiling having a slope of more than 1 1/2"/ft (41.7 mm/m). Sloping ceilings are further classified as follows:

Sloping-Peaked Type. A ceiling in which the ceiling slopes in two directions from the highest point. Curved or domed ceilings can be considered peaked with the slope figures as the slope of the chord from highest to lowest point.

Sloping-Shed Type. A ceiling in which the high point is at one side with the slope extending toward the opposite side.

Smooth Ceiling. A ceiling surface uninterrupted by continuous projections, such as solid joists, beams, or ducts, extending more than 4 in. (100 mm) below the ceiling surface. Open truss constructions are not considered to impede the flow of fire products unless the upper member in continuous contact with the ceiling projects below the ceiling more than 4 in. (100 mm).

Should. Indicates a recommendation or that which is advised but not required.

Shunt Auxiliary Alarm System. See Auxiliary Fire Alarm System.

Signal. A status indication communicated by electrical or other means.

Signaling Line Circuit (SLC). A circuit or path between any combination of circuit interfaces, control units, or transmitters over which multiple system input signals or output signals, or both, are carried.

Signaling Line Circuit Interface (SLCI). A system component that connects a signaling line circuit to any combination of initiating devices, initiating device circuits, notification appliances, notification appliance circuits, system control outputs, and other signaling line circuits.

Signaling Line Circuit Loop. The physical wire loop along which addressable input and/or output devices are connected.

Signal Silence. A function which causes participating fire alarm activated notification appliances or other outputs to deactivate without otherwise affecting the overall state of the system.

Signal Transmission Sequence. A DACT that obtains dial tone, dials the number(s) of the DACR, obtains verification that the DACR is ready to receive signals, transmits the signals, and receives acknowledgment that the DACR has accepted that signal before disconnecting (going on-hook).

Silence Inhibit. The ability of a fire alarm control unit to prevent the signal silence button from operating until after a prescribed amount of time.

Single Station Alarm. A detector comprising an assembly incorporating a sensor, control components, and an alarm notification appliance in one unit operated from a power source either located in the unit or obtained at the point of installation.

Single Station Alarm Device. An assembly incorporating the detector, the control equipment, and the alarm-sounding device in one unit operated from a power supply either in the unit or obtained at the point of installation.

Site-Specific Software. Software that defines the specific operation and configuration of a particular system Typically, it defines the type and quantity of hardware modules, customized labels, and specific operating features of a system.

Smoke Alarm. A single or multiple station alarm responsive to smoke.

Smoke Barrier. A continuous membrane, either vertical or horizontal, such as a wall, floor, or ceiling assembly, that is designed and constructed to restrict the movement of smoke. A smoke barrier might or might not have a fire resistance rating. Such barriers might have protected openings.

Smoke Compartment. A smoke compartment is a space within a building enclosed by smoke barriers on all sides, including the top and bottom. In the provision of smoke compartments utilizing the outside walls or the roof of a building, it is not intended that outside walls or roofs or any openings therein are capable of resisting the passage of smoke.

Smoke Detector. A device that detects visible or invisible particles of combustion.

Solenoid. A coil of wire so arranged around a core of air, iron, or other material to transform electrical energy to mechanical energy.
Solid Joist Construction. Refers to ceilings having solid structural or solid nonstructural members projecting down from the ceiling surface for a distance of more than 4 in. (100 mm) and spaced at intervals 3 ft (0.9 m) or less, center to center.

Spacing. A horizontally measured dimension related to the allowable coverage of fire detectors.

Spark. A moving ember. The overwhelming majority of applications involving the detection of Class A and Class D combustibles with radiant energy-sensing detectors involve the transport of particulate solid materials through pneumatic conveyor ducts or mechanical conveyors. It is common in the industries that include such hazards to refer to a moving piece of burning material as a "spark" and to systems for the detection of such fires as "spark detection systems".

Spark/Ember Detector. A radiant energy fire detector that is designed to detect sparks or embers, or both. These devices are normally intended to operate in dark environments and in the infrared part of the spectrum.

Spark/Ember Detector Sensitivity. The number of watts (or fraction of a watt) of radiant power from a point source radiator, applied as a unit step signal at the wavelength of maximum detector sensitivity, necessary to produce an alarm signal from the detector within the specified response time.

Spot-Type Detector. A device in which a detecting element is concentrated at a particular location. Typical examples are bimetallic detectors, fusible alloy detectors, certain pneumatic rate-of-rise detectors, certain smoke detectors, and thermoelectric detectors.

Standard Audible Emergency Evacuation Signal. A distinctive three-pulse temporal pattern emergency evacuation signal required by NFPA 72 for all new systems installed after July 1, 1996. For a detailed description of this signal see American National Standards (ANSI) S3.41, Audible Emergency Evacuation Signal.

Standby Battery. A battery referred to as the secondary power supply, which is kept charged by the fire alarm control unit or by a separate battery charger. When primary (AC) power fails, the battery supplies power for a limited time. The time required for a standby battery to operate the fire alarm system is defined by NFPA 72-1996 1-5.2.6.

Storage Occupancy. Storage occupancies include all buildings or structures utilized primarily for the storage or sheltering of goods, merchandise, products, vehicles, or animals. Storage occupancies include barns; hangars (for storage only); bulk oil storage; parking structures; cold storage; stables; freight terminals; truck and marine terminals; grain elevators; and warehouses.

Story. The portion of a building included between the upper surface of a floor and the upper surface of the floor or roof next above.

Stratification. The phenomenon where the upward movement of smoke and gases ceases due to the loss of buoyancy.

Subscriber. The recipient of contractual supervising station signal service(s). In case of multiple, noncontiguous properties having single ownership, the term refers to each protected premises or its local management.

Subsidiary Station. A subsidiary station is a normally unattended location that is remote from the supervising station and linked by a communications channel(s) to the supervising station. Interconnection of signals on one or more transmission channels from protected premises with a communications channel(s) to the supervising station is performed at this location.

Supervising Station. A facility that receives signals and at which personnel are in attendance at all times to respond to these signals.

Supervision. The term supervised refers to monitoring of the circuit, switch, or device in such a manner that a trouble signal is received when a fault that would prevent normal operation of the system occurs.

Supervisory Service. The service required to monitor performance of guard tours and the operative condition of fixed suppression systems or other systems for the protection of life and property.

Supervisory Signal. A signal indicating the need of action in connection with the supervision of guard tours, the fire suppression systems or equipment, or the maintenance features of related systems.

Supervisory Signal-Initiating Device. An initiating device such as a valve supervisory switch, water level indicator, or low-air pressure switch on a dry-pipe sprinkler system whose change of state signals an off-normal condition and its restoration to normal of a fire protection or life safety system, or a need for action in connection with guard tours, fire suppression systems or equipment, or maintenance features of related systems.

Supplementary. As used in NFPA 72, National Fire Alarm Code, supplementary refers to equipment or operations not required by NFPA 72, National Fire Alarm Code, and designated as such by the authority having jurisdiction.

Switched Telephone Network. An assembly of communications facilities and central office equipment operated jointly by authorized service providers that provides the general public with the ability to establish transmission channels via discrete dialing.

System Unit. The active subassemblies at the central station utilized for signal receiving, processing, display, or recording of status change signals; a failure of one of these subassemblies causes the loss of a number of alarm signals by that unit.
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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.