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A
Ampere - A unit of measure of electrical current.
AC
see Alternating Current.
Acceptance Angle
The largest angle that a guided ray of light is accepted by a fiber optic cable.
Access Method
The rules by which a network device gains the rights to transmit a communication
on the network. Common methods include carrier sense multiple access with
collision detection, token passing, and demand priority.
ACR
see Attenuation Crosstalk Ratio.
Alternating Current
An electric current that cyclically reverses the direction of flow. Frequency is
the rate at which a full cycle occurs in one second.
Amplitude
The maximum value of a varying signal.
Amplitude Modulation
One of three basic methods (see also Frequency and Phase Modulation) of adding
information to a sine wave signal in which the magnitude of the signal is varied
to impose information on it.
ANSI
American National Standards Institute
Analog Signal
An electrical signal that varies continuously without having discrete values (as
with a "digital" signal).
AppleTalk
Apple Computer's networking scheme, integrated into most Apple system software,
that allows Apple computing systems to participate in peer to peer computer
networks and to also access the services of AppleTalk servers. See also
LocalTalk.
ARCnet
Attached Resource Computer Network. A relatively low speed form of LAN data link
technology (2.5 Mbps) developed by Datapoint, in which all systems are attached
to a common coaxial cable. ARCnet uses a token-bus form of medium access control
in which a system transmits only when it has the token
Asynchronous
Transmission where sending and receiving devices are not synchronized. Data must
carry signals to indicate data division.
Asynchronous Transfer Mode (ATM)
A form of very fast packet switching in which data is carried in fixed length
units called "cells". Each cell is 53 bytes in length, with 5 bytes used as a
header in each cell. ATM employs mechanisms that can be used to set up virtual
circuits between users, in which a pair of users appear to have a dedicated
circuit between them. ATM is defined in specifications from the ITU and ATM
Forum.
Attachment Unit Interface.
The IEEE 802.3 standard name for the cable connecting an Ethernet transceiver
(MAU) to a networked device. An AUI cable is equipped with a 15-pin connector
that mates with a 15-pin connector on the networked device.
Attenuation
The decrease in magnitude of a signal as it travels through any transmission
medium such as a cable or optical fiber. Measured in dB per unit of length.
Attenuation Crosstalk Ratio (ACR)
The difference between attenuation and crosstalk, measured in dB, at a given
frequency. A quality factor for cabling to assure that signal sent down a
twisted pair is stronger at the receiving end of the cable than any interference
imposed on the same pair by crosstalk from other pairs.
Audio
Used to describe the range of frequencies within range of human hearing;
approximately 20 to 20,000 Hz.
AUI
see Attachment Unit Interface.
AWG
American Wire Gage - A wire diameter specification. The smaller the AWG number,
the larger the wire diameter.
Backbone
A cable connection between telecommunication or wiring closets, floor
distribution terminals, entrance facilities, and equipment rooms either within
or between buildings. In star networks, the backbone cable interconnects hubs
and similar devices, as opposed to cables running between hub and station. In a
bus network, the bus cable.
Backreflection
The light reflected back towards the source from the fiber optic ends and
deformations.
Backscattering
Refers to light diffraction at microscopic non-uniformities in the index of
refraction of the optical fiber causing backreflection of optical power towards
the source.
Balanced Cable, Balanced Line
A cable having two identical conductors that carry voltages of opposite
polarities and equal magnitude with respect to ground. The conductors are
twisted to maintain balance over a distance.
Balanced Transmission
A mode of signal transmission in which each conductor carries the signal of
equal magnitude, but opposite polarity. A 5 volt signal for example, appears as
a +2.5 Volts on one conductor and -2.5 Volts on the other.
Balun
An impedance matching transformer that converts the impedance of one interface
to the impedance of another interface. Generally used to connect balanced
twisted pair cabling with unbalanced coaxial cabling. The term is derived from
"balanced / unbalanced".
Bandpass
A range of frequencies or wavelengths within which a component operates.
Baseband
A transmission method in which the entire bandwidth of the transmission medium
is used to transmit a single digital signal. The signal is driven directly onto
the transmission medium without modulation of any kind. Baseband is simpler,
cheaper and less sophisticated than Broadband.
Bandwidth
The range of frequencies required for proper transmission of a signal. Expressed
in Hertz (cycles per second). The higher the bandwidth, the more information
that can be carried. A continuous range starting from zero is said to be
"baseband", while a range starting substantially above zero is "broadband".
Baud
The number of changes in signal per second. A given baud rate does not
necessarily transmit an equal number of bits/sec. For example, a signal with
four voltage levels may be used to transfer two bits of information for every
baud.
Beacon
A special frame in Token-Ring systems indicating a serious problem with the ring
such as a break.
Bel
A unit that represents the logarithm of the ratio of two levels.
Bend Loss
A form of increased attenuation in an optical fiber caused by an excessively
small bend radius. The attenuation may be permanent if microfractures caused by
the bend continue to affect transmission of the light signal.
Bend Radius
Radius of curvature that a fiber optic or metallic cable can bend before the
risk of breakage or increased attenuation occurs.
BER
see Bit Error Rate
BICSI
Building Industry Consulting Service International.
Binder
A tape or thread used to hold assembled cable components in place.
BISDN
Broadband ISDN
Bit
One binary digit.
Bit Error Rate
A measure of data integrity, expressed as the ratio of received bits that are in
error, relative to the amount of bits received. Often expressed as a negative
power of ten.
Bit Stream
A continuous transfer of bits over some medium.
Bit Stuffing
A method of breaking up continuous strings of 1 bits by inserting a 0 bit. The 0
bit is removed at the receiver.
Bit Time
The length of time required to transmit one bit of information.
BL
Blue.
BNC
A coaxial connector that uses a "bayonet" style turn and lock mating method.
Used with RG-58 or smaller coaxial cable. Used with 10Base2 Ethernet thin
coaxial cable. BNC is an acronym for Bayonet-Neill-Concelman.
Bonding
A method used to produce good electrical contact between metallic parts. Also
refers to the grounding bars and straps used in buildings to bond equipment to
an approved ground.
BPS
Bits per second.
BR
Brown.
Braid
Fine wires interwoven to form a tubular flexible structure that may be applied
over one or more wires for the purpose of shielding. May also be formed into a
flattened conductor to be used as a grounding strap.
BRI
ISDN Basic Rate Interface
Bridged Tap
Multiple appearances of the same cable pair at several distribution points.
Broadband
A transmission facility having a bandwidth sufficient to carry multiple voice,
video or data channels simultaneously. Each channel occupies (is modulated to) a
different frequency bandwidth on the transmission medium and is demodulated to
its original frequency at the receiving end. Channels are separated by
"guardbands" (empty spaces) to ensure that each channel will not interfere with
its neighboring channels. This technique is used to provide many CATV channels
on one coaxial cable.
Broadcast
Sending data to more than one receiving device at a time.
Buffer
A protective coating over a strand of optical fiber.
Bus Topology
1. In general, a physical layout of network devices in which all devices must
share a common medium to transfer data, and no two devices may transmit
simultaneously. 2. With LANs, a linear network topology in which all computers
are connected to a single cable.
Butyl Rubber
A synthetic rubber with good electrical insulating properties.
Byte
A group of 8 bits.
c
A small "c" is the symbol for the speed of light in a vacuum.
C
A capital "C" is the designation for celsius.
Cable
A group of insulated conductors enclosed within a common jacket.
Cable Sheath
A covering over the conductor assembly that may include one or more metallic
members, strength members, or jackets.
Campus
The buildings and grounds of a complex, such as a university, college,
industrial park or military establishment.
Capacitance
The ability to store electric charge between two conductors separated by a
dielectric material. Capacitance is expressed in Farads.
Carrier
An electrical signal of a set frequency that can be modulated in order to carry
data.
Carrier Detect
A circuit that detects the presence of a carrier.
Carrier Sense
With Ethernet, a method of detecting the presence of signal activity on a common
channel.
Carrier Sense Multiple Access with Collision Detect
A network access method used by Ethernet in which a station listens for traffic
before transmitting. If two stations transmit simultaneously, a collision is
detected and both stations wait a brief time before attempting to transmit
again.
Category 1, Cat 1
Unshielded twisted pair used for transmission of audio frequencies. Used as
speaker wire, door bell wire, etc. Not suitable for networking applications.
Category 2, Cat 2
Unshielded twisted pair used for transmission at frequencies up to 1.5 Mhz. Used
in analog telephone applications. Not suitable for networking applications.
Category 3, Cat 3
Unshielded twisted pair with 100 ohm impedance and electrical characteristics
supporting transmission at frequencies up to 16 MHz. Defined by the TIA/EIA
568-A specification.
Category 4, Cat 4
Unshielded twisted pair with 100 ohm impedance and electrical characteristics
supporting transmission at frequencies up to 20 MHz. Defined by the TIA/EIA
568-A specification.
Category 5, Cat 5
Unshielded twisted pair with 100 ohm impedance and electrical characteristics
supporting transmission at frequencies up to 100 MHz. Defined by the TIA/EIA
568-A specification.
Category 5e, Cat 5e, Enhanced Cat 5, Cat 5+
Category 5e is a new standard that will specify transmission performance that
exceeds Cat 5. Cat 5e has improved specifications for NEXT, PSELFEXT, and
Attenuation. Like Cat 5, it consists of unshielded twisted pair with 100 ohm
impedance and electrical characteristics supporting transmission at frequencies
up to 100 MHz. To be defined in the TIA 568-A-5 update.
Category 6, Cat 6
Category 6 is a proposed standard that aims to support transmission at
frequencies up to 250 MHz over 100 ohm twisted pair.
Category 7, Cat 7
Category 7 is a proposed standard that aims to support transmission at
frequencies up to 600 MHz over 100 ohm twisted pair.
CATV
Community antenna television, or "Cable TV". CATV is a broadband transmission
facility which generally uses a 75 Ohm coaxial cable to carry numerous
frequency-divided TV channels simultaneously.
CBX
Computerized Branch Exchange.
Cellular Polyethylene
Expanded or "foam" polyethylene, a material with a reduced dielectric constant
consisting of individual closed cells of inert gas suspended in a polyethylene
medium.
CDDI
Copper Distributed Data Interface - A version of FDDI that uses copper wire
media instead of fiber optic cable.
Channel
The end to end transmission path between two points at which application
specific equipment is connected.
Channel Insertion Loss
For fiber optic links, the static loss of a link between a transmitter and
receiver. It includes the loss of the fiber, connectors, and splices.
Characteristic Impedance
The impedance that an infinitely long transmission line would have at its input
terminal. If a transmission line is terminated in its characteristic impedance,
it will appear (electrically) to be infinitely long, thus minimizing signal
reflections from the end of the line.
Cheapernet
Another name for thin Ethernet or 10Base2 systems.
Chirping
Refers to the change of optical frequency of laser diodes when the laser diode
is pulsed between two different optical power levels. Chirp broadens the laser's
spectral width causing chromatic dispersion.
Chromatic Dispersion
Synonym for "material dispersion".
Circuit
1. A system of conducting media designed to pass a signal or voltage between two
points. 2. A bi-directional communications path between two pieces of associated
equipment.
Cladding
The material surrounding the core of a fiber optic cable. The cladding must have
a lower index of refraction than the core in order to contain the light in the
core.
Class A
ISO/IEC 11801 designation for twisted pair cabling rated to 100 KHz. Used in
voice and low frequency applications. Comparable to Category 1 cabling. Not
suitable for networking applications
Class B
ISO/IEC 11801 designation for twisted pair cabling rated to 1 MHz. Used in
medium bit rate applications. Comparable to Category 2 cabling. Not suitable for
networking applications
Class C
ISO/IEC 11801 designation for twisted pair cabling rated to 16 MHz. Used in high
bit rate applications. Corresponds to TIA/EIA Category 3 cabling.
Class D
ISO/IEC 11801 designation for twisted pair cabling rated to 100 MHz. Used in
very high bit rate applications. Corresponds to TIA/EIA Category 5 cabling.
Class E
ISO/IEC proposal for twisted pair cabling rated to 250 MHz. Corresponds to the
proposed TIA/EIA Category 6 cabling standard.
Closet
An enclosed space for housing telecommunications and networking equipment, cable
terminations, and cross-connect cabling. It contains the horizontal cross
connect where the backbone cable cross-connects with the horizontal cable.
Coating
Material surrounding the cladding of the fiber for protection.
Coax, Coaxial Cable
A type of communication transmission cable in which a solid center conductor is
surrounded by an insulating spacer which in turn is surrounded by a tubular
outer conductor (usually a braid, foil or both). The entire assembly is then
covered with an insulating and protective outer layer. Coaxial cables have a
wide bandwidth and can carry many data, voice and video conversations
simultaneously.
Coherence
Refers to the phase stability of two wavetrains, from the same optical wave,
separated in time
Collision
When electrical signals from two or more devices sharing a common data transfer
medium crash into one another. This commonly happens on Ethernet type systems.
Conduit
A rigid or flexible metallic or nonmetallic raceway of circular cross section in
which cables are housed for protection and to prevent burning cable from
spreading flames or smoke in the event of a fire.
Conductivity
The ability of a material to allow the flow of electrical current. It is the
reciprocal of resistivity. Measured in "mhos" (ohms backwards).
Conductor
A material that offers low resistance to the flow of electrical current.
Continuity
An uninterrupted pathway for electrical signals.
Cord
A very flexible insulated cable.
Core
The central region of an optical fiber through which light is transmitted.
Coupling ratio
The percentage of optical power transfered to the secondary output port of a
coupler relative to the total power of the primary and the secondary output
ports.
CRC
see Cyclic Redundancy Check
Critical angle
The angle at the interface between core and cladding where a guided ray in the
core undergoes total internal reflection.
Cross Connect
A facility enabling the termination of cable elements and their interconnection,
and/or cross-connection, primarily by means of a patch cord or jumper.
Cross Connection
A connection scheme between cabling runs, subsystems, and equipment using patch
cords or jumpers that attach to connecting hardware at each end.
Crossover
A conductor which connects to a different pin number at each end.
Crossover Cable
A twisted pair patch cable wired in such a way as to route the transmit signals
from one piece of equipment to the receive signals of another piece of
equipment, and vice versa.
Crosstalk
The coupling of unwanted signals from one pair within a cable to another pair.
Crosstalk can be measured at the same (near) end or far end with respect to the
signal source.
CSA
Canadian Standards Association
CSMA/CD
see Carrier Sense Multiple Access with Collision Detect.
Current
The flow of charge in a conductor. See "alternating current" and "direct
current".
Current Loop
A two wire transmit/receive interface.
Customer Premises
Buildings, offices, and other structures under the control of a
telecommunications customer.
Cutoff Wavelength
A distinct boundary, in the wavelength spectrum, which characterizes the mode of
operation of a fiber. A fiber operating at wavelengths lower than the cutoff
wavelength is multimode while the same fiber operating at wavelengths higher
than cutoff wavelength is single mode.
Cut-through Resistance
The ability of a material to withstand mechanical pressure without damage.
Cyclic Redundancy Check (CRC)
An error checking technique used to ensure the accuracy of transmitting digital
code over a communications channel. The transmitted messages are divided into
predetermined lengths which, used as dividends, are divided by a fixed divisor.
The remainder of the calculation is appended onto and sent with the message. At
the receiving end, the computer recalculates the remainder. If it does not match
the transmitted remainder, and error is detected.
D Connector
see Subminiature D Connector
Data Connector
A four position connector for 150-ohm STP used primarily with Token-Ring
networks.
Data Grade
A term used for twisted-pair cable used in networks to carry data signals. Data
grade media has a higher frequency rating than voice grade media used in
telephone wiring.
DAS
Dual Attachment Station. Term used with FDDI networks to denote a station that
attaches to both the primary and secondary rings.
dB
Decibel. A unit for measuring the relative strength of a signal. Usually
expressed as the logarithmic ratio of the strength of a transmitted signal to
the strength of the original signal. A decibel is one tenth of a "bel".
DB-9
Nine pin D connector.
DB-15
Fifteen pin D connector.
DB-25
Twenty-five pin D connector.
DC
see Direct Current.
DCE
Data Communications Equipment. Any equipment that connects to Data Terminal
Equipment (DTE) to allow transmission between DTEs.
DC Loop Resistance
The total DC resistance of a cable. For twisted pair cable, it includes the
round trip resistance, down one wire of the pair and back up the other wire.
Demand Priority
A network access method used by 100VG-AnyLAN. The hub arbitrates requests for
network access received from stations, assigning access based on priority and
traffic loads.
Demarcation Point
A point where the operational control or ownership changes, such as the point of
interconnection between telephone company facilities and a user's building or
residence.
DGM
Data Grade Media (see Data Grade)
Dielectric
An insulating (non-conducting) material.
Dielectric Constant
The property of a dielectric which determines the amount of electrostatic energy
that can be stored by the material when a given voltage is applied to it. Also
called permattivity.
Digital Signal
An electric signal which possesses two distinct states (on/off,
positive/negative, one/zero).
Direct Current
An electric current that flows in one direction and does not reverse direction
as with "alternating current".
Dispersion
The phenomenon in an optical fiber whereby light photons arrive at a distant
point in different phase than they entered the fiber. Dispersion causes receive
signal distortion that ultimately limits the bandwidth and usable length of the
fiber cable. The two major types of dispersion are 1) mode (or modal) dispersion
caused by differential optical path lengths in a multimode fiber, and 2)
material dispersion caused by differing transmission times of different
wavelengths of light in the fiber optic material.
Distortion
Any undesired change in a wave for or signal.
Distribution Frame
A structure with terminations for connecting the permanent cabling of a facility
in a manner that interconnections or cross connects may be readily made.
DIW
Direct Inside Wire. Twisted pair wire used inside a building, usually two or
four pair AWG 26.
Drain Wire
An uninsulated wire in contact with a shield throughout its length. Used to
terminate the shield.
Drop Cable
The cable which allows connection and access to and from the trunk cables of a
network such as the cables that connect individual PCs to the bus on a bus LAN.
In a CATV system, the transmission cable from the distribution cable to a
dwelling.
DS1/DS3
see T1 and T3
DTE
Data Terminal Equipment. Any piece of equipment at which a communications path
begins or ends.
Duct
1. A single enclosed raceway for wires or cable. 2. An enclosure in which air is
moved.
Duplex
1. (data communications) A circuit used to transmit signals simultaneously in
both directions. 2. (general) Two receptacles or jacks in a common housing which
accepts two plugs.
E1/E3
The European versions of T1 and T3. E1 runs at 2.048 Mbps and E3 runs at 34
Mbps.
Earth
A term for zero reference ground.
EC
European Community
ECMA
European Computer Manufacturer's Association. A European trade organization that
issues its own standards and is a member of the ISO.
EIA
Electronic Industry Association (formerly RMA or RETMA). An association of
manufacturers and users that establishes standards and publishes test
methodologies.
Electromagnetic Coupling
The transfer of energy by means of a varying magnetic field. Inductive coupling.
Electromagnetic Field
The combined electric and magnetic field caused by electron motion in
conductors.
Electromagnetic Interference
An interfering electromagnetic signal. Network wiring and equipment may be
susceptible to EMI as well as emit EMI.
Electrostatic
Electrical charge that exists when the charge is at rest.
Electrostatic Coupling
The transfer of energy by means of a varying electrostatic field. Capacitive
coupling.
ELFEXT
Equal Level Far End Crosstalk
EMI
see Electromagnetic Interference.
Encoding
A means of combining clock and data information into a self-synchronized stream
of signals.
Entrance Facility
An entrance to a building for both public and private network service cables
(including antennae) including the entrance at the building wall and continuing
to the entrance room or space.
Entrance Point
The point of emergence of telecommunications conductors through an exterior
wall, a concrete floor slab, or from a rigid metal conduit or intermediate metal
conduit.
Entrance Room
A space in which the joining of inter- or intra-building telecommunications or
networking backbone facilities takes place. An entrance room may also serve as
an equipment room.
Equipment Room
An enclosed area housing telecommunications and network equipment, distinguished
from the telecommunications or wiring closet by its increased complexity and
presence of active equipment.
EPDM
Ethylene-propylene-diene monomer rubber. A material with good insulating
properties.
EPR
Ethylene-propylene copolymer rubber. A material with good insulating properties.
Ethernet
A local area network (LAN) protocol defined in the IEEE 802.3 standard in which
computers access the network through a Carrier Sense Multiple Access / Collision
Detect (CSMA/CD) protocol.
f
Frequency
Farad
A unit of capacitance that stores one coulomb of electrical charge when one volt
of electrical pressure is applied.
Far End Cross Talk (FEXT)
Crosstalk that is measured on the quiet line at the opposite end as the source
of energy on the active line. FEXT is not typically measured in cabling, with
Near End Cross Talk (NEXT) being the preferred crosstalk measurement.
Fast Ethernet
Ethernet standard supporting 100 Mbps operation.
FCC
Federal Communications Commission.
FCS
Frame Check Sequence. Error detection field.
FDDI
Fiber Distributed Data Interface. An ANSI Standard (ANSI X3T12) for a 100 Mbps
token passing network based on fiber-optic (FDDI) and twisted-pair (CDDI)
cabling.
Feeder Cable
In a CATV system, the transmission cable from the head end (signal pickup) to
the trunk amplifier. Also called a trunk cable.
FEP
Fluorinated ethylene propylene. A thermoplastic with excellent dielectric
properties which is often used as insulation in fire rated cables.
FEXT
see Far End Cross Talk
Fiber Optics
The technology in which communication signals in the form of modulated light
beams are transmitted over a glass fiber transmission medium. Fiber optic
technology offers high bandwidth, small space needs and protection from
electromagnetic interference, eavesdropping and radioactivity.
Fifty-pin Connector
Commonly referred to as a Telco, CHAMP, or blue ribbon connector, this connector
is used on Ethernet 10Base-T hubs as an alternate twisted-pair segment
connection method. The 50-pin connector connects to 25-pair cables, which are
frequently used in telephone wiring systems and which typically meet Category 3
specifications.
Fillers
Nonconducting components cabled with the insulated conductors or optical fibers
to impart roundness, flexibility, tensile strength, or a combination of all
three.
Floating
Refers to a circuit that has no connection to ground.
FOIRL
Fiber Optic Inter-Repeater Link. An Ethernet fiber optic connection method
intended for connection of repeaters.
Frequency
The number of times a periodic action occurs in a unit of time. Expressed in
hertz (abbreviated Hz). One hertz equals one cycle per second.
Frequency Division Multiplexing (FDM)
A technique for combining many signals on a single circuit by dividing the
available transmission bandwidth by frequency into narrower bands, each used for
a separate communication channel.
Frequency Modulation (FM)
One of three basic methods (see also Amplitude and Phase Modulation) of adding
information to a sine wave signal in which its frequency is varied to impose
information on it.
Frequency Response
The range of frequencies over which a device operates as expected.
FTP
see Screened Twisted Pair (ScTP) cable
Full Duplex Transmission
Data transmission over a circuit capable of transmitting in both directions
simultaneously.
G
Green
Gbps
Gigabits per second.
Giga
A prefix meaning one billion
Gigahertz (GHz)
One billion hertz.
GIPOF
Graded Index Plastic Optical Fiber
Graded Index Fiber
A multimode fiber optic cable design in which the index of refraction of the
core is lower toward the outside of the core and progressively increases toward
the center of the core, thereby reducing modal dispersion of the signal.
Ground
A common point of zero potential such as a metal chassis or ground rod.
Ground Loop
A condition where an unintended connection to ground is made through an
interfering electrical conductor.
Half Duplex Transmission
Data transmission over a circuit capable of transmitting in either direction,
but not simultaneously.
HC
see Horizontal Cross Connect.
Headend
The equipment in a cable system which receives the various program source
signals, processes them, and retransmits them to subscribers.
Headroom
The amount by which a cable ACR exceeds 10dB.
Hertz
The unit of frequency, one cycle per second (abbreviated Hz).
HF
High Frequency
Home Run
A cable run that connects a user outlet directly with the telecommunications or
wiring closet, with no intermediate splices, bridges, taps, or other
connections.
Horizontal Cabling, Horizontal Wiring
The portion of the cabling system that extends from the work area outlet to the
horizontal cross connect in the telecommunications or wiring closet.
Horizontal Cross Connect
A cross connect of horizontal cabling to other cabling, e.g. horizontal,
backbone, or equipment.
Host
Computer that offers services on a network.
Hub
A hardware device that contains multiple independent but connected modules of
network and internetworking equipment. Hubs can be active (where they repeat
signals set to them) or passive (where they do not repeat but merely split
signals sent through them). Hub may also refer to a repeater, bridge, switch,
router, or any combination of these.
HVAC
Heating, ventilation, and air conditioning system.
Hybrid Cable
An assembly of two or more cables (of the same or different types or categories)
covered by one overall sheath.
Hypalon
A DuPont trade name for a synthetic rubber (chlorosulfonated polyethylene) used
as insulating and jacketing material for cabling.
I
Symbol used to designate current.
IC
see Intermediate Cross Connect.
ICEA
Insulated Cable Engineers Association
ICS
IBM Cabling System
IDC
Insulation Displacement Contact/Connector
IDF
Intermediate Distribution Frame. This is usually located on each floor within a
building. It is tied directly to the Main Distribution Frame via cables.
IEC
International Electrotechnical Commission
IEEE
Institute of Electrical and Electronics Engineers. A professional organization
and standards body. The IEEE Project 802 is the group within IEEE responsible
for LAN technology standards.
IEEE 802.1
The IEEE standards committee defining High Level Interfaces, Network Management,
Internetworking, and other issues common across LAN technologies.
IEEE 802.2
The IEEE standards committee defining Logical Link Control (LLC).
IEEE 802.3
The IEEE standards committee defining Ethernet networks.
IEEE 802.5
The IEEE standards committee defining Token-Ring standards.
Impedance
A unit of measure, expressed in Ohms, of the total opposition (resistance,
capacitance and inductance) offered to the flow of an alternating current.
Impedance Match
A condition where the impedance of a particular circuit cable or component is
the same as the impedance of the circuit, cable, or device to which it is
connected.
Impedance Matching Transformer
A transformer designed to match the impedance of one circuit to another.
Index of Refraction
The ratio of light velocity in a vacuum to its velocity in a given transmission
medium.
Infrastructure, Telecommunications
A collection of those telecommunications components, excluding equipment, that
together provide the basic support for the distribution of all information
within a building or campus.
Interconnection
A connection scheme that provides for the direct connection of a cable to
another cable or to an equipment cable without a patch cord or jumper.
Intermediate Cross Connect
A cross-connect between 1st level and 2nd level backbone cabling.
Injection Laser Diode
A semiconductor laser in which the lasing occurs at the junction of n-type and
p-type semiconductor materials.
Insertion Loss
A measure of the attenuation of a device by determining the output of a system
before and after the device is inserted into the system. For example, a
connector causes insertion loss across the interconnection (in comparison to a
continuous cable with no interconnection).
ISDN
Integrated Services Digital Network
ISO
International Standards Organization
Isolated Ground
A separate ground conductor which is insulated from the equipment or building
ground.
Isolation
The ability of a circuit or component to reject interference.
Insulation
A material which is nonconductive to the flow of electrical current.
Interference
Undesirable signals which interfere with the normal operation of electronic
equipment or electronic transmission.
Isochronous
Signals which are dependent on some uniform timing or carry their own timing
information imbedded as part of the signal. Voice and video signals are
isochronous signals, but data transfer is generally not.
ITU
International Telecommunications Union. An international organization that
develops communications standards.
Jabber
Term used with Ethernet to describe the act of continuously sending data. A
jabbering station is one whose circuitry or logic has failed, and which has
locked up a network channel with its incessant transmission.
Jack
A female connector.
Jacket
The outer protective covering of a cable.
Jitter
The slight movement of a transmission signal in time or phase that can introduce
errors and loss of synchronization. More jitter will be encountered with longer
cables, cables with higher attenuation, and signals at higher data rates. Also,
called phase jitter, timing distortion, or intersymbol interference.
Jumper
An assembly of twisted pairs without connectors used to used to join
telecommunications circuits at the cross connect. Similar to a patch cable
(which has connectors).
Keying
The mechanical feature of a connector system that guarantees correct orientation
of a connection, or prevents the connection to a jack, or to an optical fiber
adapter, of the same type intended for another purpose.
L
Symbol used to designate inductance.
LAN
Local Area Network
LAN Adapter
see Network Interface Card
Laser
Light Amplification by Stimulated Emission of Radiation. A device which produces
light with a narrow spectral width. Used in fiber optic communication systems,
usually single mode, where high capacity and low attenuation are required.
LATA
Local Access and Transport Area.
Lay
The axial distance required for one cabled conductor or conductor strand to
complete one revolution about the axis around which it is cabled.
Lay Direction
The direction of the progressing spiral twist in while looking along the axis of
the cable away from the observer. The lay direction can be either "left" or
"right".
LCL
see Longitudinal Conversion Loss
LCTL
see Longitudinal Conversion Transfer Loss
Leakage
An undesirable passage of current over the surface of or through a connector.
Leased Line
A private telephone line rented for the exclusive use of a leasing customer,
without interchange switching arrangements.
LED
see Light Emitting Diode.
LF
Low frequency.
Light Emitting Diode
A semiconductor diode which emits incoherent light when a current is passed
through it. Used as a light source in fiber optic transmission.
Link
A transmission path between two points not including terminal equipment, work
area cables, or equipment cables.
Listed
Equipment included on a list published by an organization, acceptable to the
authority having jurisdiction, that maintains periodic inspection of production
of listed equipment, and whose listing states either that the equipment or
material meets appropriate standards or has been tested and found suitable for
use in a specified manner.
Lobe
An arm of a Token-Ring which extends from a Multistation Access Unit (MSAU) to a
workstation adapter.
LocalTalk
A low-speed form of LAN data link technology, part of Apple Computer's AppleTalk
networking scheme, that uses a carrier sense multiple access with collision
avoidance (CSMA/CA) form of medium access control. Supports transmission at 230
Kbps.
Longitudinal Coversion Loss (LCL)
Also called near-end unbalance attenuation, measures cable balance by comparing
the signal appearing across the pair to the signal applied between ground and
the pair, where the applied signal and the across pair signal are at the same
end of the cable.
Longitudinal Coversion Transfer Loss (LCTL)
Also called far-end unbalance attenuation, measures cable balance by the
comparison of the signal appearing across the pair to the signal between ground
and the pair, where the applied signal is at the opposite end of the cable from
where the across pair signal is measured.
Loopback
A type of diagnostic test in which a transmitted signal is returned to the
sending device after passing through a data communications link or network. This
test allows the comparison of a returned signal with the transmitted signal.
Loss
The portion of energy applied to a system that is dissipated and performs no
useful work.
Lossy
Having poor efficiency.
M
Mutual Inductance
mA
Milliampere (one thousandth of an ampere)
MAC
see Medium Access Control
Main Cross Connect
A cross connect for first level backbone cables, entrance cables, and equipment
cables. The main cross connect is at the top level of the premises cabling tree.
Manchester Coding
A method of LAN signal encoding in which each bit time that represents a data
bit has a transition in the middle of the bit time. Used with 10 Mbps Ethernet
(10Base2, 10Base5, 10Base-F, & 10Base-T), and Token-Ring LANs.
Material Dispersion
Dispersion that results from each wavelength traveling at a different speed than
other wavelengths through an optical fiber. Also called "chromatic dispersion".
MAU
Media Attachment Unit. The transceiver in Ethernet networks. Also a common name
for the MSAU (Multi-station Access Unit) in Token-Ring networks.
Mbaud
Megabaud. One million baud.
Mbps
Megabits per second.
MC
see Main Cross Connect
MDF
Main Distribution Frame
MDI
see Media Dependent Interface
Media
Wire, cable, or conductors used for transmission of signals.
Media Filter
An impedance matching component used in Token-Ring networks to transform the 100
ohm impedance of UTP cabling to the 150 ohm impedance of media interface
connections.
Medium Access Control (MAC)
A mechanism operating at the data link layer of local area networks which
manages access to the communications channel (medium).
Medium Dependent Interface (MDI)
In Ethernet, the connector used to make the mechanical and electrical interface
between a transceiver and a media segment. An 8-pin RJ-45 connector is the MDI
for the 10Base-T, 100Base-TX, 100Base-T2, 100Base-T4, and 1000Base-T media
systems.
Medium Independent Interface (MII)
Used with 100 Mbps Ethernet systems to attach MAC level hardware to a variety of
physical media systems. Similar to the AUI interface used with 10 Mbps Ethernet
systems. An MII provides a 40-pin connection to outboard transceivers (also
called PHY devices).
Mega
Prefix meaning one million.
Megahertz (MHz)
One million hertz.
MIC
Medium Interface Connector. Duplex fiber optic connector used with Fiber
Distributed Data Interface (FDDI) networks.
Micro
Prefix meaning one millionth.
Microfarad
One millionth of a farad. Abbreviated µF (less commonly µfd, mf, and mfd).
Micron
One millionth of a meter. Abbreviated µm.
Midsplit Broadband
A broadcast network configuration in which the cable is divided into two
channels, each using a different range of frequencies. One channel is used to
transmit signals and the other is used to receive.
MII
see Medium Independent Interface.
Mil
Unit of length equal to one thousandth of an inch (0.001 inch).
Milli
Prefix meaning one thousandth.
Mixing Segment
Ethernet term used in IEEE 802.3 standards to describe a segment that may have
more than two MDI connections.
MMF
set Multimode Fiber
Modal Dispersion
Dispersion that results from the different transit lengths of different
propagating modes in a multimode optical fiber.
Mode
A single electromagnetic wave traveling in an optical fiber.
Mode Field Diameter
The diameter of optical energy in a single mode fiber. Because the mode-field
diameter is larger than the core diameter, it replaces core diameter as a
practical parameter.
Modem
A device that implements "modulator-demodulator" functions to convert between
digital data and analog signals.
Modular Jack
The equipment mounted half of a modular interconnection. Typically a female
connector. A modular jack may be keyed or unkeyed and may have six or eight
contact positions, but not all the positions need to be equipped with jack
contacts.
Modular Plug
The cable mounted half of a modular interconnection. Typically a male connector.
A modular plug may be keyed or unkeyed and may have six or eight contact
positions, but not all the positions need to be equipped with contacts.
Modulation
Altering the characteristics of a carrier wave to convey information. Modulation
techniques include amplitude, frequency, phase, plus many other forms of digital
encoding.
MSAU
Multi-station Access Unit. Device used to interconnect lobe cables from stations
on a Token-Ring network.
MT-RJ
Proposal for a new duplex fiber optic connector standard from AMP/Siecor.
Multimode Fiber
A fiber optic cable which supports the propagation of multiple modes. Multimode
fiber may have a typical core diameter of 50 to 100 µm with a refractive index
that is graded or stepped. It allows the use of inexpensive LED light sources
and connector alignment and coupling is less critical than single mode fiber.
Distances of transmission and transmission bandwidth are less than with single
mode fiber due to dispersion.
Mutual Capacitance
Capacitance between two conductors when all other conductors are connected
together.
MV
Millivolt (one thousandth of a volt)
MW
Milliwatt (one thousandth of a watt)
Mylar
DuPont trademark for polyethylene terephtalete (polyester) film.
NA
see Numerical Aperture
N connector
A coaxial connector used for Ethernet 10Base5 thick coax segments.
Nanometer (nm)
One billionth of a meter.
Nanosecond (ns)
One billionth of a second.
NBR
Butadiene-acrylonitrile copolymer rubber, a material with good oil and chemical
resistance.
Near-End Crosstalk
Crosstalk between two twisted pairs measured at the same end of the cable as the
disturbing signal source. NEXT is the measurement of interest for crosstalk
specifications.
NEC
National Electrical Code.
NEMA
National Electrical Manufacturers Association.
Neoprene
A synthetic rubber with good resistance to oil, chemical, and flame. Also called
polychloroprene.
Network
An interconnection of computer systems, terminals or data communications
facilities.
Network Interface Card
A circuit board installed in a computing device used to attach the device to a
network. A NIC performs the hardware functions that are required to provide a
computing device with physical communications capabilities. Also Network
Interface Unit (NIU).
NEXT
see Near-End Crosstalk.
NFPA
National Fire Protection Association
Nibble
One half byte.
NIC
see Network Interface Card.
NIR
Near-end Crosstalk-to-Insertion Loss Ratio
Node
End point of a network connection. Nodes include any device connected to a
network such as file servers, printers, or workstations.
Noise
In a cable or circuit, any extraneous signal which interferes with the desired
signal.
Nomex
Dupont trademark for a temperature-resistant, flame retardant nylon.
NRZ
Non Return to Zero.
NRZI
Non Return to Zero Inverted.
Numerical Aperture (NA)
The "light gathering ability" of an optical fiber, defining the maximum angle to
the fiber axis at which light will be accepted and propagated.
NVP
Nominal Velocity of Propagation. The speed a signal propagates through a cable
expressed as a decimal fraction of the speed of light in a vacuum.
Nylon
An abrasion resistant thermoplastic with good chemical resistance.
O
Orange
OC-n
See Optical Carrier n
Octet
8 bits (also called a byte).
OFSTP
Optical Fiber Standard Test Procedure.
Ohm
The electrical unit of resistance. The value of resistance through which a
potential of one volt will maintain a current of one ampere.
Ohm's Law
Stated E=IR, I=E/R, or R=E/I, the current "I" in a circuit is directly
proportional to the voltage "E", and inversely proportional to the resistance
"R".
Optical Carrier n
Optical signal standards. The "n" indicates the level where the respective data
rate is exactly "n" times the first level OC-1. OC-1 has a data rate of 51.84
Mbps. OC-3 is 3 times that rate or 155.52 Mbps, etc. Associated with SONET.
OLTS
Optical Loss Test Set
Open
A break in the continuity of a circuit.
Optical Fiber
A thin glass or plastic filament used for the transmission of information via
light signals. The signal carrying part of a fiber optic cable.
Optical Fiber Cable
An assembly consisting of one or more optical fibers.
Optical Fiber Duplex Adapter
A mechanical media termination device designed to align and join two duplex
connectors.
Optical Fiber Duplex Connection
A mated assembly of two duplex connectors and a duplex adapter.
Optical Fiber Duplex Connector
A mechanical media termination device designed to transfer optical power between
two pairs of optical fibers.
Optical Time Domain Reflectometry.
A method for evaluating optical fiber based on detecting and measuring
backscattered (reflected) light. Used to measure fiber length and attenuation,
evaluate splice and connector joints, locate faults, and certify cabling
systems.
OSI
Open Systems Interconnection
Outside Plant
Cabling, equipment, or structures that are out of doors.
OTDR
Optical Time Domain Reflectometry.
Outlet
A connecting device in the work area on which a horizontal cable terminates.
Outlet Box
A metallic or non-metallic box mounted within a wall, floor, or ceiling used to
hold outlet, connector, or transition devices.
Output
The useful signal or power delivered by a circuit or device.
PABX
Private Automatic Branch Exchange
Packet
Bits grouped serially in a defined format, containing a command or data message
sent over a network.
PAM5x5
Signal encoding scheme used in the Ethernet 100Base-T2 and 1000Base-T media
systems.
Patch Cable, Patch Cord
A flexible piece of cable terminated at both ends with connectors. Used for
interconnecting circuits on a patch panel or cross connect.
Patch Panel
A passive device, typically flat plate holding feed through connectors, to allow
circuit arrangements and rearrangements by simply plugging and unplugging patch
cables.
Pathway
A facility for the placement of telecommunication or networking cables.
PBX
Private Branch Exchange
PC
Personal Computer
PCC
Premises Communication Cable, CSA Cable Designation.
PDN
Public Data Network
Peak
The maximum instantaneous value of a varying current or voltage.
Pedestal
A device, usually mounted on the floor, which is used to house voice/data jacks
or power outlets at the point of use. Also referred to as a monument, tombstone,
above floor fitting or doghouse.
Periodicity
Uniformly spaced variations in the insulation diameter of a transmission cable
that result in reflections of a signal.
Phase
An angular relationship between waves.
Phase Modulation (PM)
One of three basic methods (see also Amplitude and Frequency Modulation) of
adding information to a sine wave signal in which its phase is varied to impose
information on it.
Phase Shift
A change in the phase relationship between two alternating quantities.
Photodetector
Used on the receiving end of a fiber optic cable to convert light energy into
electrical energy.
PHY
Physical Layer device.
Physical Layer
Layer one of the seven layer ISO Reference Model for Open Systems
Interconnection. The physical layer is responsible for the transmission of
signals, such as electrical signals, optical signals, or radio signals, between
computing machines.
Pico
Prefix meaning one millionth of one millionth.
Picofarad
One millionth of one millionth of a farad. Abbreviated "pf".
Pin-diode
A photodetector used to convert optical signals to electrical signals in a
receiver.
Plastic
High polymeric substances, including both natural and synthetic products, but
excluding the rubbers that are capable of flowing under heat and pressure.
Plastic Fiber
An optical fiber made of plastic rather than glass.
Plasticizer
A chemical added to plastics to make them softer and more flexible.
Plenum
The air handling space between the walls, under structural floors, and above
drop ceilings used to circulate and otherwise handle air in a building. Such
spaces are considered plenums only if they are used for air handling. Work
spaces are generally not considered plenums.
Plenum Cable
A cable that is rated as having adequate fire resistance and low smoke producing
characteristics for use in air handling spaces (plenum).
Plug
A male connector.
PMD
Physical Media Dependent
POF
Plastic Optical Fiber.
Polybutadiene
A type of synthetic rubber often blended with other synthetic rubbers to improve
their properties.
Polyethylene
A thermoplastic material having excellent electrical properties.
Polymer
A substance made of repeating chemical units or molecules. The term is often
used in place of plastic, rubber, or elastomer.
Polypropylene
A thermoplastic material similar to polyethylene but somewhat stiffer and with a
higher softening point (temperature).
Polyurethane
Broad class of thermoplastic polymers with good abrasion and solvent resistance.
Can be solid or cellular (foam).
Polyvinyl Chloride (PVC)
A general purpose thermoplastic used for wire and cable insulation and plastics.
PVC is know for high flexibility. Often used in nonplenum wire insulation and
cable jackets. A modified version of the material may be found in jacketing of
some plenum rated cables.
POTS
Plain Old Telephone System
Potting
Sealing by filling with a substance to exclude moisture.
Power Level
The difference between the total power delivered to a circuit, cable, or device
and the power delivered by that device to a load.
Power Ratio
The ratio of power appearing at the load to the input power. Expressed in dB.
Premise Cabling
The entire cabling system on the user's premises used for transmission of voice,
data, video and power.
Prewiring
Wiring installed before walls and ceilings are enclosed.
Private Branch Exchange (PBX)
A private telephone switching system, usually located on a customer's premises
connecting a common group of lines from one or more central offices to provide
service to a number of individual phones. Now used interchangeably with PABX
(Private Automatic Branch Exchange).
Propagation Delay
Time required for a signal to pass from the input to the output of a device.
Protector
A device that limits damaging voltages on metallic conductors.
Protocol
A set of agree-upon rules and message formats for exchanging information among
devices on a network.
PSELFEXT
Power Sum Equal Level Far End Crosstalk
PSNEXT
Power Sum Near End Crosstalk
Public Data Network
A network established and operated for the specific purpose of Providing data
transmission services to the public.
Public Switched Network
Any common carrier network that provides circuit switching between public users,
such as the public telephone network, telex or MCI's Execunet.
Pull Strength, Pull Tension
The pulling force that can be applied to a cable without affecting the specified
characteristics of the cable.
Pulse
A current or voltage which changes abruptly from one value to another and back
to the original value in a finite length of time.
Pulse Code Modulation (PCM)
The most common method of representing an analog signal, such as speech, by
sampling at a regular rate and converting each sample to an equivalent digital
code.
PVC
Polyvinyl Chloride
PVDF
Polyvinylidene Fluoride
Quartet Signaling
The signaling method used by 100VG-AnyLAN, in which the 100 Mbps signal is
divided into four 25 Mbps channels and then transmitted over different pairs of
a cable. Category 3 cables transmit one channel on each of four pairs.
R
Symbol for Resistance
Raceway
Any channel designated for holding wires or cables. Raceways may be metallic or
nonmetallic and may totally or partially enclose the wiring. (e.g. conduit,
cable trough, cellular floor, electrical metallic tubing, sleeves, slots,
underfloor raceways, surface raceways, lighting fixture raceways, wireways,
busways, auxiliary gutters, and ventilated flexible cableways)
Radio Frequency
The frequencies in the electromagnetic spectrum that are used for radio
communications.
RBOC
Regional Bell Operating Company. One of the seven Bell operating companies that
were formed during the divestiture of AT&T.
RCDD
Registered Communication Distribution Designer. A certification of BICSI, an
industry organization, for individuals qualified to consult and design
telecommunications distribution systems.
Reactance
A measure of the combined effects of capacitance and inductance on an
alternating current. The amount of such opposition varies with the frequency of
the current. The reactance of a capacitor decreases with an increase in
frequency. The opposite occurs with an inductance.
Receiver
A device whose purpose is to capture transmitted signal energy and convert that
energy for useful functions. In fiber optic systems, an electronic component
that converts light energy to electrical energy.
Reflection
A return of electromagnetic energy that occurs at an impedance mismatch in a
transmission line, such as a LAN cable.
Refractive Index.
The ratio of the speed of light in a vacuum to its velocity in a transmitting
medium, such as an optical fiber core.
Repeater
A device that receives, amplifies (and sometimes reshapes), and retransmits a
signal. It is used to boost signal levels and extend the distance a signal can
be transmitted. It can physically extend the distance of a LAN or connect two
LAN segments.
Resistance
In dc circuits, the opposition a material offers to current flow, measured in
ohms. In ac circuits, resistance is the real component of impedance and may be
higher than the value measured at dc.
Resonance
An ac circuit condition in which inductive and capacitive interact to cause a
minimum or maximum circuit impedance.
Retractile Cord
A cord having specially treated insulation or jacket so that it will retract
like a spring. Retractibility may be added to all or part of a cord's length.
Reversed Pair
A wiring error in twisted pair cabling where the conductors of a pair are
reversed between connector pins at each end of a cable.
RF
see Radio Frequency
RFI
Radio Frequency Interference. Electromagnetic interference at radio frequencies.
RFP
Request for Proposal
RFQ
Request for Quote (or Quotation)
RG/U
Radio Grade/Universal. RG is the common military designation for coaxial cable.
Ring
1. A polarity designation of one wire of a pair indicating that the wire is that
of the secondary color of a 5-pair group (e.g. the blue white wire of the blue
pair). 2. A wiring contact to which the ring wire is attached. 3. The negative
wiring polarity (see Tip).
Ring Network
A network topology in which terminals are connected in a point-to-point serial
fashion in an unbroken circular configuration. Many logical rings are wired as a
star for greater reliability.
Ripcord
A cord placed directly under the jacket of a cable in order to facilitate
stripping (removal) of the jacket.
Riser
The conduit or path between floors of a building into which telephone,
networking, and other utility cables are placed to bring service from one floor
to another.
Riser Cable
A type of cable used in vertical building shafts, such as telecommunications and
utility shafts. Riser cable typically has more mechanical strength than general
use cable and has an intermediate fire protection rating.
RJ
A term from the telephone industry, used for jacks (connectors) that were
registered for use with particular types of telephone services. RJ stands for
"registered jack".
RJ-45
A USOC code identifying an 8-pin modular plug or jack used with unshielded
twisted pair cable. Officially, an RJ-45 connector is a telephone connector
designed for voice grade circuits only. RJ-45 type connectors with better signal
handling characteristics are called 8-pin connectors in most standards
documents, though most people continue to use the RJ-45 name for all 8-pin
connectors.
RMS
Root Mean Square.
Rope Strand
A conductor composed of groups of twisted strands.
Rubber
A general term used to describe wire insulations made of thermosetting
elastomers, such as natural or synthetic rubbers, neoprene, Hypalon, butyl
rubber, and others.
Rx
Receive
RZ
Return to Zero
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 fiber optic connector having a 2.5mm ferrule, push-pull latching mechanism,
and the ability to be snapped together to form duplex and multifiber connectors.
SC connectors are the preferred fiber 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 fiber 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).
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 Fiber
An optical fiber that will allow only one mode to propagate. The fiber has a
very small core diameter of approximately 8 µm. 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 fiber axis. Generally, a light ray that enters
the fiber 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 fiber optic connector. The 905 version is a straight ferrule
design, whereas the 906 is a stepped ferrule design.
SMF
see Single Mode Fiber
S/N
see Signal to noise ratio
SNR
see Signal to noise ratio
SONET
see Synchronous Optical Network.
Source
In fiber optics, the device which converts the electrical information carrying
signal to an optical signal for transmission over an optical fiber. A
fiber-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 (c)
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 fiber 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 Fiber
An optical fiber 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 fibers generally have lower bandwidths than graded index multimode
fibers.
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 fiber optic cable that increases the cable's tensile strength and
serves as a load bearing component. Usually made of Kevlar aramid yarn,
fiberglass 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.
T1
T1 is a 1.544 Mbps multichannel digital transmission system for voice or data
provided by long distance carriers. Also referred to as DS1 (Data Services).
T3
T3 is a 44.736 Mbps multichannel digital transmission system for voice or data
provided by long distance carriers. Also referred to as DS3 (Data Services).
Tap
On Ethernet 10Base5 thick coaxial cable, a tap is a method of connecting a
transceiver to the cable by drilling a hole in the cable, inserting a contact to
the center conductor, and clamping the transceiver onto the cable at the tap.
TC
Telecommunications Cross Connect.
TDR
See Time Domain Reflectometry
Teflon
Dupont Company trademark for flourocarbon resins (see FEP and TFE).
Telecommunications Closet
see Closet
Telecommunications Equipment Room
see Equipment Room
Terminal
1. A point at which information may enter or leave a communications network. 2.
A device by means of which wires may be connected to each other.
Terminator
A device that provides electrical resistance at the end of a transmission line.
Its function is to absorb signals on the line, thereby keeping them from
bouncing back and being received again by the network.
TFE
Tetraflouroethylene. A thermoplastic material with good electrical insulating
properties and chemical and heat resistance.
Thermal Rating
The temperature range in which a material will perform its function without
undue degradation.
Thermoplastic
A material which will soften, flow, or distort appreciably when subjected to
sufficient heat and pressure. Examples are polyvinyl chloride and polyethylene.
Thermosetting
A material which will not soften, flow, or distort appreciably when subjected to
sufficient head and pressure. Examples are rubber and neoprene.
Thicknet
Ethernet 10Base5 coaxial cable.
Thinnet
Ethernet 10Base2 coaxial cable. Also called "cheapernet".
TIA
Telecommunications Industry Association. Body which authored the TIA/EIA 568-A
"Commercial Building Telecommunications Wiring Standard" in conjunction with
EIA.
Time Division Multiplexing (TDM)
A technique for combining many signals on a single circuit by interleaving bits
or bytes of data from successive channels.
Time Domain Reflectometry
A technique for measuring cable lengths by timing the period between a test
pulse and the reflection of the pulse from an impedance discontinuity on the
cable. The returned waveform reveals many undesired cable conditions, including
shorts, opens, and transmission anomalies due to excessive bends or crushing.
The length to any anomaly, including the unterminated cable end, may be computed
from the relative time of the wave return and nominal velocity of propagation of
the pulse through the cable. See also Optical Time Domain Reflectometry.
Tinsel
A type of electrical conductor comprised of a number of tiny threads, each
having a fine, flat ribbon of copper or other metal closely spiraled about it.
Used for small size cables requiring limpness and extra-long flex life.
Tip
1. A polarity designation of one wire of a pair indicating that the wire is that
of the primary (common) color of a 5-pair group (e.g. the white-blue wire of the
blue pair). 2. A wiring contact to which the tip wire is connected. 3. The
positive wiring polarity (also see "ring").
TNC
A threaded connector used to terminate coaxial cables. TNC is an acronym for
threaded Neill-Concelman.
Token Passing
A network access method in which a station must wait to receive a special token
frame before transmitting.
Token-Ring
A local area network (LAN) protocol defined in the IEEE 802.5 standard in which
computers access the network through a token passing scheme. Uses a star-wired
ring topology.
Topology
The physical or logical interconnection pattern of a network.
Transceiver
A combination of the words TRANSmitter and reCEIVER. A transceiver is the set of
electronics that send and receive signals on the Ethernet media system.
Transceivers may be small outboard devices, or may be built into an Ethernet
port. Also called Media Attachment Unit, or MAU.
Tracer
The contrasting color coding stripe along an insulated conductor of a wire pair.
Transducer
A device for converting mechanical energy into electrical energy.
Transfer Impedance
For a specified cable length, transfer impedance relates to a current on one
surface of a shield to the voltage drop generated by this current on the
opposite surface of the shield. Transfer impedance is used to determine shield
effectiveness against both ingress and egress of interfering signals. Shields
with lower transfer impedance are more effective than shields with higher
transfer impedance.
Transmission Line
An arrangement of two or more conductors or a wave guide used to transfer a
signal from one location to another.
Transmission Media
Anything such as wire, coaxial cable, fiber optics, air or vacuum, that is used
to carry a signal.
Transmitter
A device that converts electrical signals for transmission to a distant point.
In fiber optic systems, the electronic component that converts electrical energy
to light energy.
Transition Point
A location in the horizontal cabling where flat undercarpet cable connects to
round cable.
Tree Topology
LAN topology similar to linear bus topology, except that tree networks can
contain branches with multiple nodes.
Triaxial Cable, Triax
Triax cable is coax cable with an additional outer copper braid insulated from
signal carrying conductors. It has a core conductor and two concentric
conductive shields.
Triboelectric Noise
Noise generated in a shielded cable due to variations in capacitance between the
shield and conductor as the cable is flexed.
Trunk Cable
see Feeder Cable.
TSB
Telecommunications Systems Bulletin
Turn-key
A contractual arrangement in which one party designs and installs a system and
"turns over the keys" to another party who will operate the system.
Twinaxial Cable, Twinax
A type of communication transmission cable consisting of two center conductors
surrounded by an insulating spacer which in turn is surrounded by a tubular
outer conductor (usually a braid, foil or both). The entire assembly is then
covered with an insulating and protective outer layer. It is similar to coaxial
cable except that there are two conductors at the center.
Twin-lead
A transmission line having two parallel conductors separated by insulating
material. Line impedance is determined by the diameter and spacing of the
conductors and the insulating material and is usually 300 ohms for television
receiving antennas.
Twisted Pair
A multiple conductor cable whose component wires are paired together, twisted,
and enclosed in a single jacket. Each pair consists of two insulated copper
wires twisted together. When driven as a balanced line, the twisting reduces the
susceptibility to external interference and the radiation of signal energy. Most
twisted-pair cabling contains either 2, 4, or 25 pairs of wires.
Tx
Transmit
Type N Connector
A threaded barrel constant impedance coaxial connector for large diameter cable
such as Ethernet 10Base5 thicknet cable.
Type 1
150 ohm shielded twisted pair (STP) cabling conforming to the IBM Cabling System
Specifications. Two twisted pairs of 22 AWG solid conductors for data
communications are enclosed in a braided shield covered with a sheath. Tested
for operation up to 16 MHz. Available in plenum, non-plenum, riser, and outdoor
versions.
Type 1A
Enhanced version of IBM Type 1 cable rated for operation up to 300 Mhz. Meets
electrical specifications for 150 ohm STP-A Cable as documented in the TIA/EIA
568-A standard.
Type 2
150 ohm shielded twisted pair (STP) cabling conforming to the IBM Cabling System
specifications. Two twisted pairs of 22 AWG solid conductors for data
communications are enclosed in a braided shield. Four additional pairs of 22 AWG
solid conductors for telephones are also included in the cable jacket but
outside the braided shield. Tested for operation up to 16 MHz. Available in
plenum and non-plenum versions.
Type 2A
Enhanced version of IBM Type 2 cable rated for operation up to 300 Mhz. Meets
electrical specifications for 150 ohm STP-A Cable as documented in the TIA/EIA
568-A standard.
Type 3
IBM Cabling System designation for 100 ohm unshielded twisted pair (UTP) cabling
similar to TIA/EIA Category 3 cabling. 22 AWG or 24 AWG conductors with a
minimum of two twists per linear foot. Typically four twisted pairs enclosed
within cable jacket.
Type 5
100/140 micron optical fiber cable conforming to the IBM Cabling System
specifications. Two optical fibers are surrounded by strength members and a
polyurethane jacket. Type 5J is a 50/125 micron version defined for use in
Japan.
Type 6
150 ohm shielded twisted pair (STP) cabling conforming to the IBM Cabling System
specifications. Two twisted pairs of 26 AWG stranded conductors for data
communications. Flexible for use in making patch cables. Tested for operation up
to 16 MHz. Available in non-plenum version only.
Type 6A
Enhanced version of IBM Type 6 cable rated for operation up to 300 Mhz. Meets
electrical specifications for 150 ohm STP-A Cable as documented in the TIA/EIA
568-A standard.
Type 8
150 ohm under-carpet cable conforming to the IBM Cabling System Specifications.
Two individually shielded parallel pairs of 26 AWG solid conductors for data
communications. The cable includes "ramped wings" to minimize visibility when
installed under carpeting. Tested for operation up to 16 MHz.
Type 9 150 ohm shielded twisted pair (STP) cabling conforming to the IBM Cabling System Specifications. A plenum rated cable with two twisted pairs of 26 AWG solid or stranded conductors for data communications |