Glossary

ACR (Attenuation Crosstalk Ratio) – One of the factors that limits the distance a signal may be sent through a given medium. ACR is the ratio of the power of the received signal, attenuated by the media, over the power of the NEXT crosstalk from the local transmitter, usually expressed in decibels (dB).

ADSL (Asymmetric Digital Subscriber Line) – A type of DSL in which the bandwidth of the transmission system is divided asymmetrically (or unevenly) between the two directions. The data transmission rate from the central office to the customer premise is typically a much higher bandwidth than the transmission from the customer premise to the central office.

ADSL Splitter – A filter circuit that is installed on the customer premises, providing separate connections for the wiring that will carry ADSL and regular telephone signals. The regular voice signals and the ADSL signals run on separate wire pairs inside the customer premises.

ADSL2+ (Asymmetric Digital Subscriber Line) – Similar to ADSL with extended range and increase bandwidth. See ADSL.

ATM (Asynchronous Transfer Mode) – A very high-speed transmission technology, ATM features high bandwidth, low delay, packet-like switching and multiplexing. Utilizes fixed-size cells with header and information fields.

Amplifier (or Amp) – A device that uses an active component to increase the voltage or power of a signal without distorting its waveshape.

Amplitude – The distance between high or low points of a waveform or signal. Also referred to as wave “height”.

Analog – Refers to electronic signals that vary continuously over time, representing  any complex value of voltage. Analog signals can vary at any single or combination of frequencies representing information by value and/or frequency rather than by  state (digital).

Analog TV – A term used to mean conventional broadcast television technology  (in use for the past 50+ years)

Attenuation – Loss of volume during transmission, or decrease in the power of a signal, light beam, or light wave. Measured in decibels. Opposite of gain.

AWG (American Wire Gauge) – Standard measuring gauge for nonferrous conductors (i.e., non-iron and non-steel). Gauge measures the diameter of a conductor  (thickness of cable).

Backbone Wiring – The physical/electrical interconnections between telecommunications closets and equipment rooms. Cross-connect hardware and cabling in the Main and intermediate Cross-Connects are considered part of the backbone wiring.

Bandwidth – The difference between the highest and the lowest frequencies of a transmission channel (path for information transmission). Identifies the amount of data that can be sent through a given channel. Measured in Hertz (Hz); higher bandwidth numbers mean higher data capacity.

Baseband – A baseband signal means (1) that there is only one signal or channel on the network or cable, usually occupying a bandwidth that starts at zero hertz. The signal has exclusive use of the cable or network, (2) the technique of sending a singla (analog or digital) on a medium without modulating the signal by another carrier signal.

Bass – Low-frequency audio signals below 500Hz.

Bend Radius (Fiber) – Radius of curvature that a fiber can bend without breaking. Also see Cable Bend Radius.

BICSI (Building Industry Consulting Service International) – BICSI is a non-profit professional association, for the promotion of telecom industry standards.

Bit Error Rate (BER) – In digital applications, the percentage of received bits in error to the total number of bits received. Usually expressed as a number to the power of 10. For example 10 to the fifth power means that one in every 100,000 bits transmitted will be wrong.

Bluetooth – A RF network technology intended for short range communications (less than 10 meters) in the 2.4 GHz band to connect devices such as desktop computers, wireless phones, printers, etc.

BNC connector – Short for Bayonet Neill Concelman connector, a BNC connector is typically used with the RG-58 or RG-59 coaxial cable on professional electronic equipment. The connector is bayonet-style meaning that it is put in then turned and locked in.

Broadband – A broadband network or communications medium refers to its ability to support multiple channels of information (analog or digital) typically using some form of frequency division multiplexing. The term is also used tot refer to “high speed” communications in general.

Buffer Coating – Protective material coating applied to fibers. Stated in microns.

Bus – A network topology in which nodes are connected to a single cable with terminations at each end.

Cable Assembly – A fixed length of cable with connectors installed on both ends.
Sometimes called a Patch Cord, or Patch Cable.

Cable Bend Radius – The amount of bend that can occur before a cable may sustain
damage or increased attenuation.

Cable Modem – a gateway device that connects to a cable service provider network
and converts the digital channel used for Internet data to a local area network format
such as 10BaseT Ethernet.

Category 3 (CAT3) – A Category of Performance for inside wire and cable systems.
Commonly used for voice applications and data to 10 Mbps. Defined by FCC Part 68,
ANSI/EIA/TIA-568, TIA TSB-36 and TIA TSB-40

Category 5 (CAT5) – A Category of Performance for inside wire and cable systems.
Used in support of voice and data applications requiring a carrier frequency of up to
100 MHz. Now the most common cabling being installed for LAN connectivity. Defined
by FCC Part 68, EIA/TIA-568, TIA TSB-36 and TIA TSB-40.

Category 5e, Enhanced (CAT5e) – A Category of Performance for inside wire and
cable. Used in support of signaling rates of up to 100 MHz over distances of up to
100 meters. Calls for tighter twists, electrical balancing between pairs and fewer cable
anomalies. CAT5e is intended to support 100Base-T, ATM and Gigabit Ethernet and
wiring under development.

Category 6 (CAT6) – A Category of Performance for inside wire and cable. Category
6 is intended to specify the best performance that UTP (Unshielded Twisted Pair) and
screened twisted-pair cabling can be designed to deliver based on current technology.
Used in support of signaling rates of up to 250 MHz. CAT6 is intended to support
100Base-T, ATM, 10 Gigabit Ethernet among others.

Category of Performance – Cabling and cabling component standard adopted by the
telecommunications industry.

CEDIA (Custom Electronics Design & Installation Association) – An international
trade association of companies that specialize in designing and installing electronic
systems for the home.

Cladding – The transparent material, usually glass, that surrounds the core of an
optical fiber, causing any dispersed light to be reflected back into the central core,
there by helping to maintain signal strength over long distances.

Cleaving – To cut the end of fiber at 90 degrees with as few rough edges as possible
before a fiber termination.

CO (Central Office) – Telephone company facility where subscribers’ lines are joined
to switching equipment for connection to each other, locally and long distance.
Sometimes the same as the overseas term “public exchange”.

Coaxial Cable – A cable composed of an insulated central conducting wire wrapped
in another cylindrical conductor (the shield). The whole thing is usually wrapped
in another insulating layer and an outer protective layer. A coaxial cable has great
capacity to carry vast quantities of information. It is typically used in high-speed data
and CATV applications.

Compliance – A wiring device that meets all characteristics of a standard is said to be
in compliance with that standard.

Conductor – Any substance, usually a wire or cable, that can carry an electrical
current.

Cone – The cone-shaped part of the speaker that works as a piston to cause air
motion and consequently sound.

Connecting Block – Also called a terminal block, punch down block, quick connect
block, or cross-connect block. A plastic block containing metal wiring terminals to
establish connections from one group of wires to another. Usually each wire can be
connected to several other wires in a bus or common arrangement. There are several
types of connecting blocks: 66 clip, BIX, Krone, 110, etc. A connecting block has
insulation displacement connections (IDCs), which means you don’t have to remove
insulation from around the wire conductor before you “punch it down” (terminate it).

Connector – A device that connects wires or fibers in cable to equipment or other
wires or fibers. Wire and optical connectors most often join transmission media to
equipment or cross connects. A connector at the end of a telephone cable or wire is
used to join that cable to another cable with a mating connector or to some other
telecommunications device. Note: Connectors are sometimes referred to as jacks, but
though all jacks are connectors, not all connectors are jacks.

Cross-connect – Distribution system equipment used to terminate and administer
communication circuits. In a wire cross-connect, jumper wires or patch cords are used
to make circuit connections. In an optical cross-connect, fiber patch cords are used.
The crossconnect is located in an equipment room, riser closet, or satellite closet.

Crosstalk – See Near-End Crosstalk.

CSA – Canadian Standards Association. A non-profit, independent organization which
operates a listing service for electrical and electronic materials and equipment. It
is the body that establishes telephone equipment (and other) standards for use in
Canada.

Daisy Chain – In telecommunications, a wiring method where each telephone jack in
a building is wired in series from the previous jack. Daisy chain is NOT the preferred
wiring method, since a break in the wiring would disable all jacks “down stream” from
the break. See also Home Run.

dB (Decibel) – A dB is a unit of measure of signal strength, usually the relation
between a transmitted signal and a standard signal source. Every 3 dB equals 50%
of signal strength, so therefore a 6 dB loss is a loss of 75% of total signal strength.
Decibel measurements are commonly used in acoustics.

Demarcation Point – The point of interconnection between telephone company
terminal equipment and your building wiring. The protective apparatus or wiring at a
subscriber’s premises.

Device – As distinguished from equipment. In telecommunications, a “device” is the
physical interconnection outlet. Equipment (a computer, phone, fax machine, etc.) then
plugs into the device. See also Equipment and Plug.

Digital Cable – Carries several (usually 6 or 8) conventional channels that are digitally
encoded, compressed, and modulated into one standard cable channel, This provides
a dramatic increase in the number of channels available

DNS (Domain Name Server) – A computer program that matches URL names such as,
www.suttlesoho.com, to their numeric IP address. The tables are maintained at local,
regional and global levels by various organizations.

Down Converting – Process by which a high-definition signal is converted to a
standard definition picture

Drop Wire – Outside wire pair(s) from the telco plant (cable), to a house or building for
connection to a protector.

DSL (Digital Subscriber Line) – A generic name for a family of digital lines (also
called xDSL) being provided by service providers to their local subscribers. DSL uses
sophisticated modulation schemes to pack data onto a pair of copper wires. DSL can
coexist on the same line as voice service.

DTMF (Dual Tone, Multi-Frequency) – See Tone Dial.

DTV (Digital TV) – Umbrella term encompassing High Definition television and several
other applications including standard definition television, datacasting, multicasting,
and interactivity Pair Bonding.

Efficiency – The measure of an amplifier or speaker's ability to convert input power to
work. Expressed as a percentage.

EIA (Electronic Industries Alliance) – A trade organization of manufacturers which set
standards for use of its member companies. Many associations fall under the umbrella
of EIA, though is has recently been absorbed by the TIA, or Telecommunications
Industry Association. See www.eia.org or www.tiaonline.org.

Electromagnetic Interference (EMI) – The interference in signal transmission or
reception caused by the radiation of electrical and magnetic fields.

ELFEXT (Equal Level Far End Crosstalk) – A calculated result, that is derived by
subtracting the insertion loss of the disturbing pair from the FEXT this pair induces in
an adjacent pair

Equipment – As distinguished from Device. Telecom equipment (computers, phone,
faxes, etc.) plugs into telecommunications outlets or devices. See also Device.

Epoxy Connector – A type of fiber optic connector that requires a chemical bond, or
epoxy.

Ethernet – A type of local area network used for connecting computers, printers,
workstations, terminals, etc. within the same building. Ethernet is a physical link and
data link protocol that operates over twisted pair wire and over coaxial cable at speeds
up to 10 Mbps. Ethernet LANs are being promoted by DEC, Intel and Xerox. Compare
with Token Ring.

Ferrule – A component of a fiber optic connection that holds a fiber in place and aids
in its alignment.

FEXT (Far-End Crosstalk) – A type of crosstalk which occurs when signals on one
twisted pair are coupled to another pair as they arrive at the far end of the multi-pair
cable system.

Fiber Optics – A technology in which light is used to transport information from one
point to another. More specifically, fiber optics are thin filaments of glass through
which light beams are transmitted over long distances carrying enormous amounts of
data.

Firewall – Software and/or hardware that limits outside access from the Internet to a
local area network or computer. Firewalls are the primary line of security defense for
businesses and homes.

Frequency – The number of vibrations or cycles completed by a signal in one second.
Frequency is expressed in cycles, or more commonly, Hertz (Hz).

Gateway – A device that is responsible for connecting one network to another,
typically used to connect a home LAN to the Internet via an ISP. A gateway must
convert the WAN physical layer and protocol to the LAN physical layer and protocol.
Typical examples of a gateway are a cable or DSL modem. The term gateway is often
incorrectly used to describe a router.

HDTV (High-Definition Television) – This is the highest resolution video picture
available in Digital TV. In the U.S., the 1080i and 720p formats in a 16:9 aspect ratio
are the two acceptable HDTV formats. HDTV is a component of DTV.

Headroom (also called Overhead or Margin) – The number of decibels by which a
system exceeds the minimum defined requirements. The benefit of headroom is that
it reduces the bit-error rate (BER), and provides a performance ‘safety net’ to help
ensure that current and future high speed applications will run at peak accuracy,
efficiency and throughput.

Home Network – The infrastructure, both wired and wireless, used to interconnect
products and systems in the home to support voice, data, and broadband RF
applications and to connect those systems and applications to outside services.

Home Run – Phone system wiring where the individual cables run from each phone
directly back to the central switching equipment. Home run cabling can be thought of
as “star” cabling. Every cable radiates out from the central equipment. All PBXs and
virtually all key stems work on home run wiring. See also Star Wiring, Daisy Chain.

Hub – The point on a network where circuits are connected. Also, a switching node. In
Local Area Networks, a hub is the core of a star as in ARCNET, StarLAN, Ethernet, and
Token Ring. Hub hardware can be either active or passive. Wiring hubs are useful for
their centralized management capabilities and for their ability to isolate nodes from
disruption.

Hybrid Connector – A connector containing both optical fiber and electrical
conductors.

Insertion Loss – The difference in the amount of power received before and after
something is inserted into the circuit. In optical fiber, insertion loss is the optical power
loss due to all causes, usually expressed at decibel/kilometer.

Insulation Displacement Connection (IDC) – A type of wire termination where wire
is “punched down” into a metal holder which cuts into the insulation wire and makes
contact with the conductor, causing the electrical connection to be made.

IDF (Intermediate Distribution Frame) – A metal rack designed to connect cables
and located in an equipment room or closet. Consists of components that provide the
connection between inter-building cabling and the intra-building cabling, i.e. between
the Main Distribution Frame (MDF) and individual phone wiring. There’s usually a
permanent, large cable running between the MDF and IDF. The changes in wiring are
done at the IDF. This saves confusions in wiring.

IEEE 802.3 – IEEE stands for the Institute of Electrical and Electronic Engineers,
a publishing and standards-making body responsible for many standards used in
LANs, including the 802 series. Ethernet and StarLan both follow the 802.3 standard.
Typically they transit at 10 megabits per second. This is the most common local area
network specification.

Impedance – The total opposition (i.e. resistance and reactance) a circuit offers to
the flow of alternating current. It is measured in ohms, and the lower ohmic value, the
better the quality of the conductor.

Interconnect – 1. A circuit administration point, other than a cross-connect or an
information outlet, that provides capability for routing and rerouting circuits. It does
not use patch cords or jumper wires, and typically is a jack-and-plug device used in
smaller distribution arrangements or that connects circuits in large cables to those in
smaller cables. 2. An interconnect Company is one which sells, installs, and maintains
telephone systems for end users, typically businesses.

IP (Internet Protocol) – IP is the protocol on which the Internet is based. The IP
Protocol is a standard describing software that keeps track of the Internet’s addresses
for different nodes, routes outgoing messages, and recognizes incoming messages.
It allows a packet of information to traverse multiple networks on the way to its final
destination.

ISDN (Integrated Services Digital Network) – According to AT&T, today’s public
switched phone network has many limitations; ISDN’s vision is to overcome these
deficiencies.

Jack – A receptacle used in conjunction with a plug to make electrical contact between
communication circuits. Jacks and their associated plugs are used in a variety for
connecting hardware applications including cross connects, interconnects, information
outlets, and equipment connections. Jacks are used to connect cords or lines to
telephone systems. A jack is the female component of a plug/jack connector system,
and may be standard, modified, or keyed.

Jacket – Also Cable Jacket or Sheath. The outer covering applied over internal cable
elements for protection.

LAN (Local Area Network) – A short distance network (typically within a building or
campus) used to link together computers and peripheral devices (such as printers)
under some form of standard control.

Loop – 1. Typically a complete electrical circuit. 2. The loop is also the pair of wires that
winds it’s way from the central office to the telephone set or system at the customer’s
office, home or factory (i.e., ‘premises’ in telephony terms).

Loudspeaker – An electro-acoustic transducer that converts an electrical signal to
audible sound waves.

Magnet – The device at the back of a speaker that provides a stationary magnetic field
to attract or repel the voice coil as the signal passes through it.

Mbps (Megbits per second) – One million bits per second. (Different from MBps, or a
million bytes per second.)

MDF (Main Distribution Frame) – A wiring arrangement which connects the telephone
lines coming from outside on one side and the internal lines on the other. A main
distribution frame may also carry protective devices as well as function as a central
testing point.

MHz (Megahertz) – A unit of frequency denoting one million Hertz (i.e., 1,000,000
cycles per second).

Micron – One thousandth of a millimeter, or one millionth of a meter. Can be used to
specify the core diameter of fiber optic network cable.

MMJ (Modified Modular Jack) – A six-wire modular jack with the locking tab shifted
off to the right hand side. Used in the DEC wiring system.

Modular – Equipment is said to be modular when it is made of “plug-in units” which
can be added together to make the system larger, improve the capabilities, or expand
its size.

Modulation – The process of applying an analog or digital baseband signal to a higher
frequency analog carrier signal. It is called a carrier signal because it “carries” the
baseband signal. A good example is AM radio where a radio frequency carrier signal is
modulated by a voice or music signal.

MT-RJ – A small form factor style of fiber optic connector that is defined by its high
density footprint and RJ-47 locking mechanism.

Multimode – An optical fiber designed to allow light to carry multiple carrier signals,
distinguished by frequency or phase, at the same time. (Contrasts with singlemode.)

Nanometer (nm) – One billionth of a meter. The nanometer is a convenient unit for
describing the wavelength of light.

Near-End Crosstalk (NEXT) – Electrical noise coupled from one pair of wires to
another within a multi-pair cable; same applies to pins in a connector.

Network – A network ties things together. Computer networks connect all types of
computers and computer-related things — terminals, printers, modems, door entry
sensors, temperature monitors, etc. The networks we’re most familiar with are long
distance ones, like phones and trains. Local Area Networks (LANs) connect computer
equipment within a building or campus.

Open (Fault) – Means that the circuit is not complete of the cable/fiber is broken.

Outlet – A telecommunications outlet is a single-piece cable termination assembly
(typically on the floor or in the wall), containing one or more modular telecom jacks.
Such jacks might be RJs, coaxial terminator, fiber optic couplers, etc. See also Device
and Equipment.

Part 68 Requirements – Specifications established by the FCC as the minimum
acceptable protection communications equipment must provide the telephone
network.

Patching – A means of connecting circuits via cords and connectors that can be
easily disconnected and reconnected at another point. May be accomplished by using
modular cords connected between jack fields or by patch cord assemblies that plug
onto connecting blocks.

PBX (Private Branch Exchange) – A small, privately-owned version of the phone
company’s larger telephone central switching office.

Performance – Compare with Compliance. A device can exhibit performance
characteristics without being compliant to an industry standard.

Plug – A male component of a plug/jack connector system. In premises wiring, a
plug provides the means for a user to connect communications equipment to the
communications outlet.

Polarity – The term describing which connection is positive and which is negative.

POTS (Plain Old Telephone Service) – The basic service supplying standard single line
telephones, telephone lines and access to the public switched network. Just receive
and place calls. No added features like Call Waiting or Call Forwarding.

Power Sum – A test method for four pair cable whereby the mathematical sum of pairto-
pair crosstalk from three pairs to one pair is measured.

Premise – In telecommunications, a term for the space occupied by a customer or
authorized/joint user in a building(s) on continuous or contiguous property (except
railroad rights of way, etc.) not separated by a public road or highway.

Premise Wiring System – The entire wiring system on the user’s premises, especially
the supporting wiring that connects the communications outlets to the network
interface jack.

RBOC (Regional Bell Operation Company) – Originally seven RBOCs existed, each of
which owned two or more Bell Operation Companies (BOCs). The RBOCs were carved
out of the old AT&T/Bell System during the divestiture of the Bell operating companies
from AT&T in 1984.

RCDD (Registered Communications Distribution Designer) – A professional rating
granted by BICSI (the Building Industry Consulting Service International). RCDDs have
demonstrated a superior level of knowledge of the telecommunications wiring industry
and associated disciplines.

Return Loss – A measure of the similarity of the impedance of a transmission line and
the impedance at its terminations. It is a ratio, expressed in decibels, of the power of
the out going signal to the power of the signal reflected back.

RG – Original military designations for 75-ohm coaxial cables. RG stands for Radio
Grade and was used to designate the part number of the cable.

RG-6 – The most commonly-recognized variety of RG-6 is CATV distribution coax,
used to route cable television signals to and within homes, and RG-6 type cables
have become the standard for CATV, mostly replacing the smaller RG-59, in recent
years. CATV distribution coax typically has a copper-coated steel center conductor
and a combination aluminum foil/aluminum braid shield, typically with low coverage
(about 60%). RG-6 type cables are also used in professional video applications,
carrying either baseband analog video signals or serial digital (SDI) signals; in these
applications, the center conductor is ordinarily solid copper, the shielding is much
heavier (typically aluminum foil/95% copper braid), and tolerances are more tightly
controlled, to improve impedance stability. RG-6 cables typically are fitted with some
type of connector at each end; in CATV distribution applications, these are typically F
connector style; in professional baseband video, BNC connectors; and in consumer
a/v applications other than RF and CATV, RCA plugs.

RG-59 – is a specific type of coaxial cable, often used for low-power video and RF
signal connections. The cable has a characteristic impedance of 75 ohms. It can be
used at baseband video frequencies or, for short distances, at broadcast frequencies.
Its high-frequency losses are too great to allow its use over long distances at broadcast
frequencies; in these applications, RG-6 is used instead. Typical use for these cables
are to run from your satellite dish system on the outside of your home to the satellite
TV receiver above your television.

Ring – As in Tip and Ring. One of the two wires needed to set up a telephone
connection. See Tip.

RJ (Registered Jack) – RJs are telephone and data jacks/applications registered
with the FCC. Numbers, like RJ-11, RJ-45, etc. are widely misused in the
telecommunications industry. A much more precise way to identify a jack is to specify
the number of positions (width of opening) and number of conductors. Example: “8-
position, 8-conductor jack” or “6-position, 4-conductor jack.”

RMU (Rack Mount Unit) – A standard unit of measure of utilized space on a rack (or
frame) equal to 1.75 inches in height.

SCTE (Society of Cable Telecommunications Engineers) – A non-profit professional
association for the promotion of coaxial information and standards.

Sensitivity – A measurement of the sound output of a speaker or speaker system's
output relative to the power put in. Typically measured in dB at 1 watt of input, 1 meter
away.

Series Wiring – See Daisy Chain.

Service Loop – When a device is terminated to the wire in the communications
outlet, a fair amount of “slack” should be left on the wire and wound in the box to
accommodate future trimming when devices are changed out.

Singlemode – A fiber that allows only a single mode of light to propagate. This
eliminates the main limitation to bandwidth, modal dispersion.

Sound – Acoustical energy in waves generally accepted to be between 20 and 20,000
cycles per second.

Splice – The joining of two or more cables together by connecting the conductors pair
to pair.

Standards – Agreed principles of protocol. Standards are set by committees working
under various trade and international organizations.

Standard Definition Television (SDTV) – Digital television that provides roughly the
same resolution as existing analog television.

Star Wiring/Star Topology – See Home Run.

T1 – A standard for digital transmission in North America. A digital transmission link
with a capacity of 1.544 Mbps (1,544,000 bits per second.) T1 lines are used for
connection networks across remote distances. Bridges and routers are used to connect
LANs over T1 networks.

Talk Battery – The DC voltage supplied by the central office to the subscriber’s loop,
which allows voice conversation.

TCP/IP – A set of protocols developed by the department of the defense to link
dissimilar computers across many kinds of networks.

Telco – An Americanism for Telephone Company.

Ten Base-T – See 10Base-T at end of Glossary.

Terminate – To connect a wire conductor to something, typically a piece of equipment.

TIA – Telecommunications Industry Association. A trade organization of manufacturers
which sets standards for use of its member companies. Formerly fell under the
umbrella or EIA (Electronic Industries Alliance). See www.tiaonline.org.

Tip – 1. The first wire in a pair of wires. (The second wire is called the “ring” wire.) 2.
A conductor in a telephone cable pair which is usually connected to positive side
of a battery at the telco. It is the phone industry’s equivalent of Ground in a normal
electrical circuit. See Ring.

Tone Dial – A push-button telephone dial that makes a different sound (in fact, a
combination of two tones) for each number pushed. The technically correct name for
tone dial is Dual Tone Multi Frequency, or DTMF.

Token Ring – A ring topology for a local area network (LAN) in which a supervisory
frame, or token, must be received by an attached terminal or workstation before that
terminal or workstation can start transmitting. The workstation with the token then
transmits and sues the entire bandwidth of whatever communications media the
token ring network is using. A token ring can be wired as a circle or a star, with the
workstations wired to a central wiring center, or to multiple wiring centers. The most
common wiring scheme is called a starwired ring. Whatever the wiring, a token ring LAN
always works logically as a circle, with the token passing around the circle from one
workstation to another. The advantage of token ring LANs is that media faults (broken
cable) can be fixed easily, since it’s easy to isolate the faults. Token rings are typically
installed in centralized closets, with loops snaking to served workstations.

Topology – As in network topology. The geometric physical or electrical configuration
describing a local communication network; the shape or arrangement of a system. The
most common topologies are the bus, ring and star.

TP-PMD – Twisted Pair-Physical Media Dependent. Technology under review by the ANSI
X3T9.5 working group that allows 100 Mbps transmission over twisted-pair cable.

Tweeter – A small loudspeaker responsive only to the higher acoustic frequencies and
reproducing sounds of high pitch.

Twisted Pair – Two insulated copper wires twisted around each other to reduce
induction (thus interference) from one wire to the other. The twists, or lays, are varied
in length to reduce the potential for signal interference between pairs. Several sets of
twisted pair wires may be enclosed in a single cable. In cables greater than 25 pairs,
the twisted pairs are grouped and bound together.

UL – Underwriters Laboratories, a privately owned company that tests to make
sure that products meet safety standards. UL also administers a program for the
certification of Category-Rated Cable.

USOC – Universal Service Order Code. An old Bell system term identifying a particular
service or equipment offered under tariff.

UTP (Unshielded Twisted Pair) – See Twisted Pair.

VoIP (Voice over Internet Protocol) – The technology used to transmit voice
conversations over a data network using Internet Protocol.

Watt – The basic measuring unit for electrical or acoustical power.

Workstation – The working area in a building required by one telecommunications
user. Industry standards call for one voice drop and one data drop for each
workstation. The voice drop is on 4-pair unshielded twisted pair (UTP). The data drop
may be 100W 4-pair UTP, 150W 2-pair shielded twisted pair (STP), or optical fiber.

10BASE-T – This is the IEEE standard that defines the requirement for sending
information at 10 Mbps on unshielded twisted-pair cabling, and defines various
aspects of running Ethernet on this cabling

100BASE-T – This is the IEEE standard that defines the requirement for sending
information at 100 Mbps on unshielded twisted-pair cabling, and defines various
aspects of running base band Ethernet on this cabling.

1000BASE-T – This is the proposed IEEE standard that defines the requirement for
sending information at 1000 Mbps on unshielded twisted-pair cabling, and defines
various aspects of running base band Ethernet on this cabling.