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.
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.
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".
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.
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
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.
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.
Channel
The end to end transmission path between two points at which
application specific equipment is connected.
Cheapernet
Another name for thin Ethernet or 10Base2 systems.
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.
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.
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.
CRC
see Cyclic Redundancy Check
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.
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.
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.
Crosstalk
The unwanted transfer of a signal from one circuit to another.
In twisted pair cables, the unwanted transfer of signals from
transmitting wires to other wires in the cable plant.
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
For a single-mode fiber, the wavelength above which the operation
switches from multimode to single-mode propagation.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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 Disperson
Dispersion that results from each wavelength traveling at a
different speed than other wavelengths through an optical fiber.
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 Dependent Interface (MDI)
Term used in Ethernet standards to describe the connector used
to make a physical and electrical connection between a transceiver
and a media segment. The 8-pin RJ-45 style connector is the MDI
for the 10Base-T, 100Base-TX, 100Base-T2, and 100Base-T4 Ethernet
media systems.
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 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.
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.
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.
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).
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
Plug
A male connector.
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.
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.
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.
Riser
A backbone cable running vertically between floors.
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.
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.
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 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
enclosed in a braided shield covered with a sheath.
Tested for operation up to 16 MHz.
Type 9A
Enhanced version of IBM Type 9 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.
A transmission line in which voltages on the two conductors are
unequal with respect to ground. Generally one of the conductors is
connected to a ground point. An example of an unbalanced line is a
coaxial cable.
Underground Cable
Cable that is intended to be placed beneath the surface of the
ground in ducts or conduit. Not necessarily intended for direct
burial in the ground.
Unilay
A conductor with more than one layer of helically laid wires with
the direction of lay and length of lay the same for all layers.
Unshielded Twisted Pair (UTP)
Twisted pair cabling that includes no shielding. UTP most often
refers to the 100 ohm Category 3, 4, & 5 cables specified in the
TIA/EIA 568-A standard.
USOC
Universal Service Order Code. Pronounced "U-Sock". An old Bell
System term used to identify a particular service or device offered
under tariff. Often used to refer to an old cable color code scheme
that was current when USOC codes were in use.
Volt-ampere. A designation of power in terms of voltage and current.
Vampire Tap
see Tap
Velocity of Propagation
The transmission speed of electrical energy in a length of cable
compared to speed in free space. Usually expressed as a percentage.
Test devices use velocity of propagation to measure a signal's transit
time and thereby calculate the cable's length.
VGM
Voice Grade Media (see Voice Grade)
VHF
Very high frequency. The portion of the electromagnetic spectrum
extending from 30 to 300 MHz.
Video
A signal which contains visual information, such as a picture in
a television system.
Voice Grade
A term used for twisted-pair cable used in telephone systems to
carry voice signals.
Volt
The unit of electrical potential. One volt is the electrical
potential that will cause one ampere of current to flow through one
ohm of resistance.
Voltage
Electrical potential expressed in Volts.
Voltage Drop
The voltage developed across a component by the current flow
through the resistance of the component.
A unit of electrical power. One watt is equivalent to the power
represented by one ampere of current flowing through a load with a
voltage drop of one volt in a dc circuit.
Wave Form
A graphical representation of the amplitude of a signal over time.
Wavelength
The distance between successive peaks or nodes of a wave.
WAN
Wide Area Network. A network connecting computers within very
large areas, such as states, countries, and the world.
wire fault
An error condition caused by a break in the wires or a short
between the wires (or shield) in a segment of cable.
Wiring Closet
see Closet
Work Area
That area of the premises cabling where users are located. The
area from the communications outlet to the equipment connected to the
premises cabling. Loosely, an office, cubicle, and so forth.
Workgroup
A collection of workstations and servers on a LAN that are
designated to communicate and exchange data with one another.
Workstation
A computer connected to a network at which users interact with
software stored on the network.
