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S - A UL cable type. Hard service flexible cord with thermoset insulation and jacket. Also see SO and SJ.

S band - A band of frequencies between 1,550 and 5,200 megahertz.

S meter - An instrument to measure signal strength.

S/n (signal-to-noise) ratio - Measure of noise levels of a video signal: the higher the number the better.

SAA - IBM’s system application architecture. IBM’s suite of protocols intended to foster interoperability and standard interfaces for applications in an IBM environment across all hardware architectures and operating environments.

SAE - Society of Automotive Engineers. Automotive standards body.

SAN (storage area network) - A self-contained data storage network separate from the regular data network.

Satellite equipment room - A room or wiring closet used as the central wiring hub.

Saturation (color) - The vividness of a color. It is directly related to the amplitude of the chrominance signal.

SBR - A copolymer of styrene and butadiene. Also GRS or Buna-S.

SC connector - A plastic connector with a precision ceramic or polymer ferrule designed for optical fiber subscriber channel (SC) networks. Manufactured under NIT license by various companies, it offers a non-optically disconnecting design with push-pull latching.

Scanning - The rapid movement of the election beam in a pickup device of a camera or in the CRT of a television receiver. It is formatted in a line-for-line manner across the photo sensitive surface that produces or reproduces the video picture. When referred to a video surveillance field, it is the panning or the horizontal camera motion.

Schering bridge - See BRIDGE.

Scrambling - A method of encoding data to make it look more random, resulting in lower spurious levels and easier timing recovery.

Screened twisted pair (ScTP) - 100-ohm twisted-pair cable with an overall foil shield and a drain wire typically used in Category 5 cable.

SCSI (small computer system interface) - Typically used for mass storage, i.e., hard disks.

SDI (serial data interface) - SDI cables are a type of coax used for HDTV. Comes in RG-59, RG-6 and bundled versions.

SDLC (synchronous data link control) - An IBM communications line protocol associated with SNA. SDLC provides for control of a single communications link or line, accommodates a number of network arrangements and operates in half- or full-duplex over private or switched facilities.

SDN - A small diameter multi-conductor control cable with neoprene jacket and nylon sheath over polyethylene insulation.

Secondary insulation - A nonconductive material that protects the conductor against abrasion and provides a second barrier.

Segment – (1) A length of coaxial cable made up of one or more cable sections connected together with barrel connectors or T-connectors. 2. In a LAN, a segment of coaxial trunk cable with a maximum of 1,640 feet (500 meters) of regular Ethernet and 600 feet (187 meters) of RG-58A/U Thinnet.

Segmental conductor - A stranded conductor consisting of three or more stranded conducting elements, each element having approximately the shape of the sector of a circle, assembled to give a substantially circular cross section.

Self-extinguishing - Characteristic of a material whose flame is extinguished after the igniting flame source is removed.

Semiconductor - In wire industry terminology, a material possessing electrical conduction properties that fall somewhere between conductors and insulators. Usually made by adding carbon particles to an insulator. Not the same as semiconductor materials such as silicon, germanium, etc., used for making transistors and diodes.

Semiconducting jacket - A jacket having a sufficiently low-electrical resistance so its outer surface can be kept at substantially ground potential.

Semirigid cable - Generally refers to Type MI or Type ALS that can be bent or shaped into a required configuration from coils or reels.

Semirigid PVC - A hard semi flexible polyvinylchloride compound with low plasticizer content.

Semisolid - An insulation cross-section having a partially open space between the conductor and the insulation perimeter.

Sensitive conductor - A conductor terminated to a circuit that is adversely affected by spurious signals.

Sensitivity (pickup device) - The amount of current developed per unit of incident light. It can be measured in watts with the projection of an unfiltered incandescent source of light at 2,870 K degrees to the pickup device surface area. It can be then expressed in foot candles.

Separable insulated connector - An insulated device to facilitate cable connections and separations.

Separator - Pertaining to wire and cable, a layer of insulating material such as textile, paper, Mylar, etc., which is placed between a conductor and its dielectric, between a cable jacket and the components it covers, or between various components of a multiple-conductor cable. It can be used to improve stripping qualities and/ or flexibility, or can offer additional mechanical or electrical protection to the components it separates.

SE-R - Style R residential service entrance cable.

Serial interface - An interface that requires serial transmission, or the transfer of information in which the bits composing a character are sent sequentially. Implies only a single transmission channel.

Serial transmission - A technique in which each bit of information is sent sequentially on a single channel, rather than simultaneously as in parallel transmission. Serial transmission is the normal mode for data communications. Parallel transmission is often used between computers and local peripheral devices.

Series circuit - A circuit in which the components are arranged end-to-end to form a single path for current.

Serve - A filament or group of filaments such as fibers or wires, wound around a central core.

Served wire armor - Spiral wrap of soft galvanized steel wires wrapped around a cable to afford mechanical protection and increase the cable-pulling tension characteristic.

Server - A processor that provides a specific service to the network. Examples of servers are as follows: routing servers connect nodes and networks of like architectures; gateway servers connect nodes and networks of different architectures by performing protocol conversions; and terminal servers, printer servers and file servers provide an interface between compatible peripheral devices on a LAN.

Serving - A wrapping applied over the core of a cable or over a wire.

SE - A UL cable type. Service entrance cable, 600 volts.

SEW, SEWF - A CSA cable type. Silicone rubber-insulated equipment wire.

S/FTP - Foil and braided overall shield applied over individually foil shielded twisted pairs. Also referred to as PIMF cable.

SF - A CSA cable type. Silicone rubber insulated fixture wire, solid or seven-strand conductor, 200°C.

SFF - A CSA cable type. Same as SF, except flexible stranding 150°C.

SG - A CSA cable type. Same as SW except with ground wires.

SGO - A CSA cable type. Same as SWO except with ground wires.

Shared access - In LAN technology, an access method that allows many stations to use the same (shared) transmission medium. Contended access and explicit access are two kinds of shared access methods. Contrast with DISCRETE ACCESS.

SHD - Portable mine power cable, three or four individually shielded conductors, with grounding conductors, 5 kV through 25 kV.

Sheath - A covering over the conductor assembly that may include one or more metallic members, strength members or jackets.

Shield - A sheet, screen or braid of metal, usually copper, aluminum or other conducting material placed around or between electric circuits, cables or their components to contain any unwanted radiation or to keep out any unwanted interferences.

Shield coverage - See SHIELD PERCENTAGE.

Shield effectiveness - The relative ability of a shield to screen out undesirable radiation. Frequently confused with the term shield percentage, which it is not.

Shield percentage - The physical area of a circuit or cable actually covered by shielding material, expressed in percent.

Shielded insulated splice - An insulated splice in which a conducting material is employed over the full length of the insulation for electric stress control.

Shielded line - A transmission line whose elements confine radio waves to an essentially finite space inside a tubular conducting surface called the sheath, thus preventing the line from radiating radio waves.

Shielding, power cable - A conducting layer applied to increase safety, control dielectric stresses and prevent partial discharges.

Short - A low resistance path that results in excessive current flow and often in damage.

Short-haul modem - See LINE DRIVER.

Shovel cable - Normally an SHD-GC type that supplies high-voltage (2 kV to 25 kV) power to mobile equipment.

Shrinking ratio - The ratio between the expanded diameter and recovered diameter of shrinkable products.

Shrink Temperature - The temperature that effects complete recovery of a heat shrinkable product from the expanded state.

Shrink tubing - Tubing that has been extruded, cross-linked and mechanically expanded, which when reheated or released will return to its original diameter.

Shunt - A very low-resistance component used to divert a proportion of the current.

Shunt wire - A conductor joining two parts of an electric circuit to divert part of the current.

SI - An international system of standardized units of measurement.

SIA (Security Industry Association) - Professional organization involved in CCTV, access control, computer security, and fire and burglar alarm systems.


Signal - Any visible or audio indication which can convey information. Also, the information conveyed through a communications system.

Signal cable - A cable designed to carry current of usually less than one ampere per conductor.

Signal-to-noise ratio (S/N or SNR) - A ratio of the amplitude in a desired signal to the amplitude of the noise, usually expressed in decibels (dB).

Silicon avalanche zener diodes - A solid-state junction device. These devices are very fast acting but have low energy-handling capability. Switching speed is in picoseconds. They work by shunting the surge of spike impulse around the protected circuits.

Silicone - A material made from silicon and oxygen. Can be in thermosetting Elastomer or liquid form. The thermosetting Elastomer form is noted for high-heat resistance.

Simplex (multiplexer) - A multiplexer that allows the user to look at multiscreen images or perform time multiplex recording. It cannot record multiplexer pictures while showing multiscreen pictures.

Simplex transmission - Transmission is only one direction.

Single-cable - A one-cable system in broadband LANs in which a portion of the bandwidth is allocated for send signals and a portion for receive signals with a guard band in between to provide isolation from interference.

Single-mode - Optical fiber in which only one mode of light can propagate.

Single-segment LAN - A LAN composed of only one coaxial cable segment.

Sintering - Fusion of an extruded paste or a spirally applied tape wrap insulation or jacket by the use of high heat to a homogenous continuum. Usually employed for fluorocarbon, nonextrudable materials.

SIO - Serial input/output.

SIP - Session initiation protocol.

SIS - Switchboard wiring made with cross-linked polyethylene insulation.

Sixty-six (66) type wiring - A type of distribution system cross-connect and termination hardware developed by AT&T in the mid-1950s. The 66 is part of a Western Electric product code assigned sequentially to new products.

SJ - A UL or CSA cable type. Junior hard service, rubber-insulated pendant or portable cord. Same construction as type S, but 300 V.

SJO - Same as SJ, but with oil-resistant jacket.

SJOO - Same as SJO but with oil-resistant insulation as well as an oil-resistant jacket.

SJT - A UL or CSA cable type. Junior hard service thermoplastic or rubber insulated conductors with overall thermoplastic jacket. 300 V.

SJTO - Same as SJT but oil-resistant thermoplastic outer jacket.

SJTOO - Same as SJTO but with oil-resistant insulation.

Skin effect - The tendency of alternating current, as its frequency increases, to travel only on the surface of a conductor.

Slope - The difference between attenuation at the highest frequency and at the lowest frequency in a cable system. Also called spectrum tilt.

Slope compensation - The action of an equalizer or an automatic slope-compensated amplifier.

SMDS (switched multimegabit data service) - A public, connectionless, packet-switched data service that provides LAN-like performance and features over a metropolitan or wide area.

SMF - Single-mode fiber.

SMS (short message service) - Text service used with wireless networks.

SNA (systems network architecture) - The network architecture developed by IBM.

SN238 - The system 85 interface; a 4-port circuit pack.


SNM - Shielded nonmetallic sheathed cable.

SNMP (simple network management protocol software) - A computer program or set of computer programs held in some kind of storage medium and loaded into read/write memory (RAM) for execution. Compare with firmware and hardware.

SO - A UL or CSA cable type. Hard service cord, same construction as type S except oil-resistant thermoset jacket, 600 V.

SOFT WIRE - Wire that has been drawn or rolled to final size and then heated (annealed) to remove the effects of cold working.

SOHO - Small office/home office.

SOLEF - Solvay’s trademark for its PVDF polymer.

Solid conductor - A conductor consisting of one wire.

SONET (Synchronous Optical NETwork) - An emerging broadband fiber network formed by a family of network elements that conform to the SONET interface requirements. SONET is a transport network of synchronously multiplexed tributary signals. The basic electrical signal of SONET runs at a rate of 51,840 Mbps. SONET grows in multiples of the basic signal into the multigigabit range.

SOO - Same as SO but with oil-resistant insulation.

SOOW - A UL or CSA cable type. Portable cord and control cable. 600 V. Same as SOO but UL Listed or CSA Certified for outdoor use.

Source coupling loss - Loss of light intensity as the light from a source passes into an optical fiber.

SP-1 - A UL cable type. All thermoset, parallel-jacketed, two-conductor light duty cord for pendant or portable use in damp locations, 300 V.

SP-2 - Same as SP-1, but heavier construction, with or without a third conductor for grounding purposes, 300 V.

SP-3 - Same as SP-2, but heavier construction for refrigerators or room air conditioners, 300 V.

Spacer cable - A type of overhead power distribution cable. Spacing is accomplished by ceramic or plastic hangers suspended from a support messenger.

SPAN - In flat conductors, distance between the reference edge of the first and the last conductor. In

Span line - The T1 line facility between two locations.

SPC - Statistical process control.

Specific inductive capacity (SIC) - Dielectric constant of an insulating material.

SPID (service ptttt- A unique identifier that is programmed into ISDN devices in order for them to operate properly.

Spiral shield - A metallic shield of fine stranded wires applied spirally rather than braided.

Spiral stripe - A color coding stripe applied helically to the surface of an insulated wire or cable.

Spiral wrap - The helical wrap of a tape or thread over a core.

SPL (sound pressure level) - The acoustic pressure reference for the dB. The minimum threshold of undamaged human hearing is 0 dB SPL. The threshold of pain of undamaged human hearing is 120 dB SPL.

Splice - The physical connection of two or more conductors to provide electrical continuity.

Splitter - A passive device used in a cable system to divide the power of a single input into two or more outputs of lesser power. Can also be used as a combiner when two or more inputs are combined into a single output.

Spot filter - A small insert used in a lens to increase the f-stop range of the lens.

SPT - A UL type of thermoplastic-insulated, two- or three-conductor parallel cord. Frequently called “zip cord” or “lamp cord.”

Squirrel cage motor - An induction motor having the primary winding (usually the stator) connected to the power and a current is induced in the secondary cage winding (usually the rotor).

SR - Silicone rubber cable 600 V, 125°C.

SRG - A cable with ozone-resistant silicone rubber insulation with an overall jacket of braided glass yarn impregnated with flame-, heat- and moisture-resistant finish. 150/200°C 600 V appliance and motor lead wire.

SRGK - A cable with ozone-resistant silicone rubber insulation with braided glass yarn conductor jacket. Cable core of insulated conductors shielded or unshielded and an overall jacket of braided K-fiber impregnated with flame-, heat- and moisture resistant finish. 150/200°C 600 V multiconductor cable.

SRK - A cable with ozone-resistant silicone rubber insulation with an overall jacket of braided K-fiber impregnated with flame-, heat- and moisture-resistant finish. 200°C 600 V fixture wire and power cable.

SRL (structural return loss) - A measure of the variation of impedance down a length of cable.Impedance variations cause a return reflection of a portion of a signal’s energy back to the transmitter, which looks like noise.

SSH (secure shell) - A type of secure network access software used on a gateway computer. Provides a safe way to access a private network over the Internet.

SSID (service set identifier) - An identifier used in wireless LAN (WLAN) applications.

SSL (secure socket layer) - A cryptographic protocol for securing data on the Internet.

ST - A UL cable type. Hard service cord, jacketed, same as type S except thermoplastic construction. 600 V, 60°C to 105°C.

ST1 - Smoke Test #1. An optional rating for UL Listed cable types that also pass the Limited Smoke requirements contained in UL Standards. A cable that meets the requirement can be marked “ST1.”

Stability factor - The difference between the percentage power factor at 80 volts/mil and at 40 volts/mil measured on wire immersed in water at 75°C for a specified time.

Standard - A set of rules or protocols that describe how a device should be manufactured, so it will maintain interoperability (compatibility) with others of the same type from different manufacturers.

Standard Ethernet - An IEEE 802.3 compliant Ethernet network composed of standard Ethernet cable as opposed to thin Ethernet cable.

Standby UPS - A UPS system that normally connects your equipment to the normal AC power line with the batteries and inverter in standby mode. When the power line is weak or fails, it transfers the load to the batteries and inverter without any load malfunction and without any user action. When the power line returns to normal, the load is automatically retransferred back to the AC power line.

Standing wave - The stationary pattern of waves produced by two waves of the same frequency traveling in opposite directions on the same transmission line. The existence of voltage and current maxima and minima along a transmission line is a result of reflected energy from an impedance mismatch.

Standing wave ratio (swr) - A ratio of the maximum amplitude of a standing wave stated in current or voltage amplitudes.

Star - A network topology consisting of one central node with point-to-point links to several other nodes. Control of the network is usually located in the central node or switch, with all routing of network message traffic performed by the central node.

Start bit - In asynchronous transmission, the first bit used to indicate the beginning of a character, normally, a space condition which serves to prepare the receiving equipment for the reception and registration of the character.

Static charge - An electrical charge that is bound to an object. An unmoving electrical charge.

Station - 1. A network node. 2. The customer location or customer equipment.

Station adapter - An active device used to connect PC/ workstations that have transceiver connectors to thin-wire Ethernet cable.

Station cable - The part of the distribution system that begins at a cross-connect in either an equipment room or serving closet and terminates at the user room.

Station protector - A gas discharge, carbon block or other device that short circuits harmful voltages to ground in the event of lightning strikes on the phone line.

ST connector - A plastic or metal connector with a precision ceramic, polymer, or stainless steel straight tip (ST) ferrule and bayonet-style latching.

Stay cord - A component of a cable, usually a high-tensile textile, used to anchor the cable ends at their points of termination and to keep any pull on the cable from being transferred to the electrical connections.

Step index fiber - A multimode optical fiber consisting of a core of uniform refractive index, surrounded by cladding of slightly lower refractive index.

Stiffness - As applied to copper, the property of a conductor that causes it to resist permanent deformation by bending.

STO - A North American flexible cord type. Same as ST but with an oil-resistant thermoplastic outer jacket, 600 V, 60°C.

STOO - Same as STO but with oil-resistant insulation.

STOOW - Same as STOO but suitable for use in wet locations.

Stop bit - In asynchronous transmission, the last bit used to indicate the end of a character; normally a mark condition which serves to return the line to its idle or rest state.

Stop bits - One or two bits in an asynchronous communication to indicate the end of the transmission. In ISN, one of the endpoint options which can be specified for an AIM port. The option can be set to either one or two stop bits.

Stop joint - A splice that is designed to prevent any transfer of dielectric fluid between the cables being joined.

STP (spanning tree protocol) - A fault tolerance protocol. Allows multiple paths to be created between a pair of LAN segments but keeps only a primary path open. When a primary path fails an alternate path will be activated to maintain the connection.

Straight joint - A cable splice used for connecting two lengths of cable, each of which consists of one or more conductors.

Strain gauge - A device for determining the amount of strain (change in dimension) when a stress is applied.

Strain hardening - An increase in hardness and strength caused by plastic deformation at temperatures lower than the recrystallization range.

Strand - One of the wires of any stranded conductor.

Stranded conductor - A conductor composed of a group of wires, usually twisted, or of any combination of such groups of wires.

Strand lay - The distance of advance of one strand of a spirally stranded conductor, in one turn, measured longitudinally. Also referred to as lay length.

Stress-relief cable - Cable used to relieve stresses in the process of welding pipe joints by inducing heat in pipe sections to be welded, flexible copper strand.

Stress-relief cone (termination) - A device used to relieve the electrical stress at a shielded cable termination; generally used above 2,400 volts.

Strip - To remove insulation from a wire or cable.

Structural return loss- Backward reflected energies from uneven parts of the cable structure.

Subchannel - A frequency subdivision created from the capacity of one physical channel by broadband LAN technology. Bands of frequencies of the same or different sizes are assigned to transmission of voice, data, or video signals. Actual transmission paths are created when each assigned band is divided, using FDM, into a number of subchannels.

Subrate - A customer channel transmission rate less than 64 kbps. Examples: 2.4, 4.8, 9.6, 19.2 kbps.

Subscriber - A customer.

Substrate - Insulating material layer on a printed wiring board.

Suggested working voltage - AC voltage that can be applied between adjacent conductors.

Superconductors - Materials whose resistance and magnetic permeability are virtually zero at very low temperatures.

Suppressor - A device used to reduce or eliminate unwanted voltages in electric or electronic circuits. For example, a resistance conductor in, or a resistor in series with, a sparkplug cable, to suppress interference that would otherwise affect radio reception in and near the vehicle.

Surface resistivity - The resistance of a material between two opposite sides of a unit square of its surface. It is usually expressed in ohms.

Surge - A temporary and relatively large increase in the voltage or current in an electric circuit or cable. Also called transient.

Surge protector - A device that plugs between the phone system and the commercial AC power outlet. It is designed to protect the phone system from high-voltage spikes (surges) that might damage the phone system. When a surge occurs on the power line, the surge protector sends the overload to ground.

SV - A North American cable type. Vacuum cleaner cord, two or three conductor, rubber insulated. Overall rubber jacket. For light duty in damp locations, 300 V 60°C.

SVO - A North American cable type. Same as SV except oil-resistant thermoset jacket, 300 V 60°C or 90°C.

SVT - A North American cable type. Same as SV except thermoplastic jacket. 300 V, 60°C or 90°C.

SVTO - A North American cable type. Same as SVT, except with oil-resistant thermoplastic jacket, 60°C.

SW - A CSA cable type. Rubber jacketed power supply cable (8 AWG to 2 AWG) 600 V.

SWR - Standing wave ratio. The ratio of incoming to reflected energy in a cable system. See also VSWR.

Sweep test - A test to check attenuation at a range of frequencies.

Sync - Synchronous.Electronic pulses that are inserted in the video signal for the purpose of assembling the picture information in the correct position.

Synchronization - Maintaining a constant phase relationship between AC signals.

Synchronous transmission - Transmission in which there is a constant time between successive bits, characters or events. The timing is achieved by sharing of clocking.

SYS - System.

System 75 - An AT&T digital PBX that provides voice and data transport for small- to medium-sized offices.

System 85 - An AT&T digital PBX that provides voice and data transport for medium- to large-sized offices.