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SAS - Single Attachment Station. Term used with FDDI networks
to denote a station that attaches to only one of two rings in
a dual ring environment.
SBR - A copolymer of styrene and butadiene. Also GR-S
or Buna-S. Most commonly used type of synthetic rubber.
SC Connector - A fibre optic connector having a 2.5mm ferrule,
push-pull latching mechanism, and the ability to be snapped
together to form duplex and multifibre connectors. SC connectors
are the preferred fibre optic cable for premises cabling, and
are recommended by the TIA/EIA-568-A Standard for structured
cabling. Used with Ethernet 100Base-FX and 1000Base-LX/SX fibre
optic media systems.
Scanner - A cable testing device which uses TDR methods
to detect cable transmission anomalies and error conditions.
Screen - see Shield
Screened Twisted Pair (ScTP) cable - Four pair UTP, with
a single foil or braided screen surrounding all four pairs in
order to minimize EMI radiation or susceptibility. Screened
twisted pair is sometimes called Foil Twisted Pair (FTP). ScTP
can be thought of as a shielded version of the Category 3, 4,
& 5 UTP cables.
Screened/Shielded Twisted Pair (SSTP) - Four pair cabling,
with each pair having its own individual Shield, in addition
to an overall shield surrounding all four pairs. SSTP offers
similar performance to Type 1 STP except with 4 pairs (rather
than 2) and in a 100 ohm impedance (rather than 150). Associated
with Category 7.
ScTP - see Screened Twisted Pair cable
SDH - see Synchronous Digital Hierarchy.
Segment - On Ethernet a media segment may be made up
of one or more cable sections joined together to produce a continuous
cable for carrying Ethernet signals.
Semiconductor - In wire industry terminology, a material
possessing electrical conductivity that falls somewhere between
that of conductors and insulators. Usually made by adding carbon
particles to an insulator. Not the same as semiconductor materials
such as silicon, germanium, etc.
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 utilized
to improve stripping qualities, flexibility, or can offer additional
mechanical or electrical protection to the components it separates.
Sheath - see Jacket
Shield - A metallic foil or multiwire screen mesh that
is used to prevent electromagnetic fields from penetrating or
exiting a transmission cable. Also referred to as a "screen".
Shield Coverage - The physical area of a cable that is
actually covered by shielding material, often expressed as a
percentage.
Shield Effectiveness - The relative ability of a shield
to screen out undesirable interference. Frequently confused
with the term shield coverage.
Shielded Twisted Pair (STP) - A type of twisted pair
cable in which the pairs are enclosed in an outer braided shield,
although individual pairs may also be shielded. STP most often
refers to the 150 ohm IBM Type 1, 2, 6, 8, & 9 cables used
with Token Ring networks.
Signal - The information conveyed through a communication system.
Signal to noise ratio - The ratio of received signal level to
received noise level, expressed in dB. Abbreviated S/N. A higher
S/N ratio indicates better channel performance.
Silicone - General Electric trademark for a material
made from silicone and oxygen. Can be in thermosetting elastomer
or liquid form. The thermosetting elastomer form is noted for
high heat resistance.
Silver Satin - The name for the silver-gray voice-grade
patch cable used to connect a telephone to a wall jacket. Typical
silver satin patch cables do not have twisted pair wires, which
makes them unsuitable for use in LAN applications. The lack
of twisted pairs will result in high levels of crosstalk.
Simplex Transmission - Data transmission over a circuit
capable of transmitting in one preassigned direction only.
Single Mode Fibre - An optical fibre that will allow
only one mode to propagate. The fibre has a very small core
diameter of approximately 8 �m. It permits signal transmission
at extremely high bandwidth and allows very long transmission
distances.
Single-ended - An unbalanced circuit or transmission
line, such as a coaxial cable transmission line (see also Balanced
Line).
Sinusoidal - A signal which varies over time in proportion
to the sine of an angle. Ordinary alternating current is sinusoidal.
Skew Rays - A ray that does not intersect the fibre axis.
Generally, a light ray that enters the fibre at a very high
angle.
Skin Effect - The tendency of alternating current to travel
on the surface of a conductor as the frequency increases.
SMA Connector - A threaded type fibre optic connector.
The 905 version is a straight ferrule design, whereas the 906
is a stepped ferrule design.
SMF - see Single Mode Fibre
S/N - see Signal to noise ratio
SNR - see Signal to noise ratio
SONET - see Synchronous Optical Network.
Source - In fibre optics, the device which converts the
electrical information carrying signal to an optical signal
for transmission over an optical fibre. A fibre-optic source
may be a light emitting diode or laser diode.
Spectral Bandwidth - The difference between wavelengths
at which the radiant intensity of illumination is half its peak
intensity.
Spectrum - Frequencies that exist in a continuous range
and have a common characteristic. A spectrum may be inclusive
of many spectrums (e.g. the electromagnetic radiation spectrum
includes the light spectrum, radio spectrum, infrared spectrum,
etc.)
Speed of Light - In a vacuum, 299,800,000 meters per second.
Splice - A joining of conductors generally from separate
sheaths.
Splice Closure - A device used to protect a cable or
wire splice.
Split Pair - A wiring error in twisted pair cabling where
one of a pair's wires is interchanged with one of another pair's
wires. Split pair conditions may be determined with a transmission
test. Simple DC continuity testing will not reveal the error,
because the correct pin-to-pin continuity exists between ends.
However, the error may result in impedance mismatch, excessive
crosstalk, susceptibility to interference, and signal radiation.
SRL - see Structural Return Loss
SSTP, S/STP - see Screened/Shielded Twisted Pair
ST Connector - Designation for the "straight tip"
connector developed by AT&T. This fibre optic connector
features a physically contacting non-rotating 2.5mm ferrule
design and bayonet connector-to-adapter mating. Used with Ethernet
10Base-FL and FIORL links.
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
to the minimum amplitude of a standing wave stated in current
or voltage amplitudes.
Star Network - A network in which all stations are connected
through a single point.
Star Topology - A topology in which each outlet/connector
is wired directly to the distribution device.
Static Charge - An electrical charge that is bound to
an object. An unmoving electrical charge.
Station - A unique, addressable device on a network.
Stay Cord - A component of a cable, usually of high tensile
strength, used to anchor the cable ends at their points of termination
and keep any pull on the cable from being transferred to the
electrical conductors.
Step Index Fibre - An optical fibre in which the core
is of uniform refractive index with a sharp decrease in the
index of refraction at the core-cladding interface. Step index
multimode fibres generally have lower bandwidths than graded
index multimode fibres.
Step Insulated - Process of applying insulation in two
layers. Typically used in shielded networking cables such that
the outer layer of insulation can be removed and remaining conductor
and insulation can be terminated in a RJ-45 type connector.
Stitching - The activity of terminating multiconductor cables
on a punchdown block.
STP - see Shielded Twisted Pair
STP-A - Refers to the enhanced IBM Cabling System specifications
with the Type "A" suffix. The original IBM Type 1,
2, 6, & 9 specifications were designed to support operation
of 4 and 16 Mbps Token-Ring. The enhanced Type 1A, 2A, 6A, &
9A cable specifications were designed to support operation of
100 Mbps FDDI signals over copper.
Strain Gauge - A device for determining the amount of
strain (change in dimensions) when a stress is applied.
Strength Member - That part of a fibre optic cable that increases
the cable's tensile strength and serves as a load bearing component.
Usually made of Kevlar aramid yarn, fibreglass filaments, or
steel strands.
Structural Return Loss (SRL) - A measure of the impedance
uniformity of a cable. It measures energy reflected due to structural
variations in the cable. A higher SRL number indicates better
performance (more uniformity and lower reflections).
Structured Wiring - Telecommunications cabling that is
organized into a hierarchy of wiring termination and interconnection
structures. The concept of structured wiring is used in the
common standards from the TIA and EIA.
STS-n -Synchronous Transport Signal-n (see Optical Carrier-n).
Subminiature D Connector - A family of multipin data connectors
available in 9, 15, 25 and 37 pin configurations. Sometimes
referred to as DB9, DB15, DB25 and DB37 connectors respectively.
Surge - A temporary and relatively large increase in
the voltage or current in an electric circuit or cable. Also
called transient.
Surge Suppression - The process by which transient voltage
surges are prevented from reaching sensitive electronic equipment.
Sweep Test - Pertaining to cable, the frequency response
is verified by generating an rf voltage whose frequency is swept
repeatedly through a given frequency range at a rapid constant
range. The cable response is observed on an oscilloscope. The
structural return loss sweep test measures the magnitude of
internal cable reflections. A high structural return loss is
desirable.
Synchronous - Transmission in which the data character
and bits are transmitted at a fixed rate with the transmitter
and receiver being synchronized.
Synchronous Digital Hierarchy (SDH) - International standard
for optical digital transmission at hierarchical rates from
155 Mbps to 2.5 Gbps and beyond.
Synchronous Optical Network (SONET) - A USA standard
for optical digital transmission at hierarchical rates from
155 Mbps to 2.5 Gbps and beyond. |
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