|
| A |
|
|
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.
Top
|
|
| B |
|
|
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. |
Back
reflection
|
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 back reflection 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”. |
Band
pass
|
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 micro fractures
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 “guard bands” (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.
Top
|
|
| C |
|
|
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 wave trains, 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 transferred 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.
Top
|
|
| D |
|
|
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.Top |
|
| E |
|
|
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.
Top
|
|
| F |
|
|
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.
Top
|
|
| G |
|
|
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.
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|
|
| H |
|
|
Half
Duplex Transmission
|
Data
transmission over a circuit capable of transmitting in either direction,
but not simultaneously. |
HC
|
see
Horizontal Cross Connect. |
Head
end
|
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.
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|
|
| I |
|
|
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
Electro technical 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.
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| J |
|
|
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).
Top
|
|
| K |
|
|
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.
Top
|
|
| L |
|
|
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
Conversion 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
Conversion 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.
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|
|
| M |
|
|
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. |
|
| N |
|
|
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)
|
Butadiene-acrylonitrile
copolymer rubber, a material with good oil and chemical resistance. |
NBR
|
One
billionth of a second. |
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.
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