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Organization and Standards
A device that enables, any or all of the following: 1) different sizes
or types of plugs to mate with one another or to fit into a telecommunications
outlet, 2) the rearrangement of leads, 3) large cables with numerous wires
to fan out into smaller groups of wires, and 4) interconnection between
An electronic component used to increase the strength of a transmitted
analog signal. Performance is measured in deciBels (dB). Similar to a repeater
in digital systems.
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. ANALOG A mode of transmission
in which information is represented by a continuously variable electrical
A nominally continuous electrical signal that varies in amplitude or
frequency in response to changes in the physical quantity (such as sound)
that it represents.
A reduction in strength or deterioration of an electrical signal as
it passes through a transmission medium. Attenuation generally increases
with frequency, cable length and the number of connections in a circuit.
Attenuation is measured in deciBels (dB). In optical fiber, a diminution
of the signal as a function of length traveled.
AWG (American Wire Gauge)
A unit of measure used to describe the cross sectional area of a conductor.
A panel, usually made of plywood, fixed to a wall and used for mounting
Generally, the more permanent part of a communications network which
carries the heaviest traffic. Usually a vertical arrangement that connects
floors in a multi-story building. However, the same function may be served
by a lateral backbone for horizontal distribution in a low-wide building.
A range of frequencies between two predetermined limits.
In electrical transmission systems, the range between the highest and
lowest frequencies of a transmission channel. A measure of the information
capacity of the transmission channel. Bandwidth varies with the type and
method of transmission. Bandwidth is measured in Hertz (Hz, cycles per
A transmission method in which the entire bandwidth of the transmission
medium is used to transmit a single digital signal. The signal is ascribed
directly onto the transmission medium without modulation of any kind. Simultaneous
transmissions can be achieved through time division multiplexing. Baseband
is simpler, cheaper and less sophisticated than Broadband.
A measurement of the signaling speed of a data transmission device.
The speed in baud is equal to the number of times the line condition (frequency,
amplitude, voltage or phase) changes per second. If each signal event represents
only one bit, then the baud rate is the same as the bit rate; if each signal
event represents more than one bit, the baud rate is less than the bit
The smallest unit of information (data) and the basic unit in data communications.
A bit can have a value of zero or one (a mark or a space).
Bits per second. A measure of speed or data rate. Often combined with
metric prefixes such as Kbps (kilo or thousands of bits per second) and
Mbps (mega or millions of bits per second).
A bayonet-locking connector used to terminate coaxial cables. BNC is
an acronym for Bayonet-Neill-Concelman.
1. To connect one circuit or component to another in parallel. When two single line phones share the same line they are said to be bridged.
2. The interconnection or equipment used between two networks using
the same communication protocols, transmission methods and addressing structure.
Compare with gateway, which connects LANs using different protocols.
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 to ensure that each channel won't interfere
with its neighboring channels. This technique is used to provide 50 CATV
channels on one coaxial cable.
1. A data path shared by many devices. 2. A linear network topology
in which all workstations are connected to a single cable. On a bus network,
such as Ethernet, all workstations receive all transmissions; only the
workstation that the information is addressed to will use the information.
Contrast with ring and star.
A collection of bits operated upon as a unit, usually 8 bits long. Often
used to represent one character. Also used to measure the capacity of storage
devices. (1K byte = 1024 bytes)
1. A company which provides transmission services. 2. A continuous electrical
signal capable of being modified to carry information. The carrier carries
no information until some component of the signal (amplitude, frequency
or phase) is changed. These changes convey the information. (See also Amplitude
Modulation, Frequency Modulation and Phase Modulation.)
CATV(Community Antenna Television)
A method of delivering high quality television reception by transmitting
signals from a central antenna throughout the community, via coaxial cable.
CATV is a broadband transmission facility which generally uses a 75 Ohm
coaxial cable to carry numerous frequency-divided TV channels simultaneously.
CCTV (Closed Circuit Television)
In general, a video channel which is broadcast to a limited number of
locations. Often used in security applications.
Any electrical or electromagnetic communications path, either physical
or logical, between two communicating units.
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.
1. (Communications) A bi-directional communications path between two
pieces of associated equipment. 2. (Power) An arrangement of conductors,
devices and utilization equipment (loads) such that current will pass through
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
Equipment used to transform analog voice signals to digital signals
(coder) and digital signals to analog signals (decoder). May be in the
digital PBX or in the phone itself.
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.
A device used to control the input/output operations between the host
computer and a group of terminals.
A facility enabling the termination of cable elements and their interconnection,
and/or cross-connection, primarily by means of a patch cord or jumper.
A connection scheme between cabling runs, subsystems, and equipment
using patch cords or jumpers that attach to connecting hardware on each
A wiring configuration that permits two DTE devices or two DCE devices
A conductor which connects to a different pin number at each end.
The phenomenon in which a signal transmitted on one circuit or channel
of a transmission system creates an undesired effect in another circuit
or channel, generally related to wire placement, shielding, and transmission
DCE-- DATA CIRCUIT-TERMINATING EQUIPMENT / DATA COMMUNICATIONS EQUIPMENT
The interface equipment sometimes needed to connect the data terminal
equipment (DTE) to a transmission circuit or channel. Synonymous with modem.
DDS-- DATAPHONE DIGITAL SERVICE
A private, leased line digital service offered by DATAPHONE AT&T
DIGITAL SERVICE which eliminates the need for modems.
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 material that is nonmetallic and non-conductive. Generally used to
describe the insulating material surrounding the center conductor of a
A discontinuous signal. One whose state consists of discrete elements,
representing very specific information, usually on or off, one or zero.
A LAN that uses a shared communications medium (such as bus or ring
LAN) and uses shared access methods.
DTE-- DATA TERMINAL EQUIPMENT
Any form of computer equipment, peripheral or terminal capable of originating or receiving data over a communications channel.
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 2 plugs.
(Electromagnetic Interference/Radio Frequency Interference)
The interference in signal transmission or reception resulting from the radiation of Frequency Interference undesirable electrical or magnetic and electrical fields.
A baseband local area network used for connecting computers and terminals,
etc., within the same building. Ethernet was marketed (and trademarked)
by Xerox and developed jointly by Digital Equipment Corporation, Intel
and Xerox. It is the basis for the IEEE Standard 802.3.
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.
The interconnection between two networks with different communications
A unit of frequency equal to one billion Hertz (1,000,000,000 Hertz).
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 dispersion of the signal.
The conductor used to connect the grounding electrode to the building's
main grounding busbar.
A conductor or group of conductors (usually a rod, pipe, or plate) in
direct contact with the earth, providing a low impedance connection to
HALF DUPLEX TRANSMISSION
Data transmission over a circuit capable of transmitting in either direction,
but not simultaneously.
A preliminary procedure, usually part of a communications protocol,
to establish a connection between devices.
A unit of frequency equal to one cycle per second.
A pathway or cable between two locations without a point of access in
The cabling between and including the telecommunications outlet/connector
and the horizontal cross-connect.
HORIZONTAL CROSS CONNECT (HC)
A cross-connect of horizontal cabling to other cabling, eg. horizontal,
The central computer in a data communications system which provides
the primary data processing functions such as computation, data base access,
special programs or programming languages.
An assembly of 2 or more cables, of the same or different types or categories,
covered by one overall sheath.
A unit of measure, expressed in Ohms, of the total opposition (resistance,
capacitance and inductance) offered to the flow of an alternating current.
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.
1. A shared boundary. A physical point of demarcation between two devices
where the electrical signals, connectors, timing and handshaking are defined.
2. The procedures, codes and protocols that enable two entities to interact
for a meaningful exchange of information.
INTERMEDIATE CROSS-CONNECT (IC)
A cross-connect between 1st level and 2nd level backbone cabling.
A CCITT Standard, currently under development, that will cover a wide
range of data communications issues, but primarily the total integration
of voice and data. Already having major effects on exchange and multiplexer
A separate ground conductor which is insulated from the equipment or building ground.
The SI unit of energy, work, or quantity of heat. One Joule is the energy
expended when a force of one newton is applied over a displacement of one
meter in the direction of the force.
An assembly of twisted pairs without connectors, used to join telecommunications circuits/links at the cross-connect.
LAN-- LOCAL AREA NETWORK
A non-public data communications network confined to a limited geographic area (usually within a few miles), used to provide communication between computers and peripherals. The area served may consist of a single building, a cluster of buildings, or a campus-type arrangement. It is owned by its user, includes some type of switching technology and does not use common carrier circuits - although it may have gateways or bridges to other public or private networks.
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.
A private telephone line rented for the exclusive use of a leasing customer,
without interchange switching arrangements.
LED (Light Emitting Diode)
A semiconductor diode which emits light when a current is passed through
it. In lightwave transmission systems, LEDs or lasers are used as light
A signal converter that conditions the digital signal transmitted by
an RS232 interface to ensure reliable transmission beyond the 50 foot RS232
limit and often up to several miles; it is a baseband transmission device.
Also called a baseband modem, limited distance modem or short haul modem.
The communications circuit or transmission path connecting two points,
not including terminal equipment, work area cables, and equipment cables.
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
MHz (Mega Hertz)
A unit of frequency equal to one million Hertz (1,000,000 Hertz).
METROPOLITAN AREA NETWORK (MAN)
An extended LAN operating within a metropolitan area and provides an
integrated set of services for real-time data, voice and image transmission.
A desktop personal computer that serves a single user.
A unit of length equal to one millionth of a meter. (.000001 meter).
Short for micrometer.
MODEM (MOdulator DEModulator)
A device which converts digital signals to analog signals (and vice-versa)
for transmission over the telephone network, which usually is analog.
A device used in place of the pair of modems normally needed to connect
a local terminal and computer. It allows DTE to DTE data and control signal
connections not easily achieved by standard cables and connectors.
The process of varying some characteristic (See Amplitude Modulation,
Frequency Modulation or Phase Modulation) of the electrical carrier wave
to impose information on it.
An optical fiber cable containing two or more fibers, each providing
a separate information channel.
An electronic device which is used to combine several signals for transmission
over one communications channel by varying the physical characteristics
(frequency, amplitude or phase) or timing of the signals to prevent them
from interfering with each other.
A unit of length equal to one billionth of a meter (.000000001 meter).
An interconnection of computer systems, terminals or data communIcations
A formalized definition of the structure and protocols of a computer
The point of interconnection between telephone company communications
facilities and terminal equipment, protective apparatus or wiring at a
In general, any point of interconnection to a network where service
is provided, used or communication channels are interconnected.
A device which allows the connection of two DTE devices by emulating
the physical connections of a DCE device.
A group of bits, including address, data and control elements, that
are switched and transmitted together.
A data transmission method whereby data is transmitted in packets through
a network to a remote location. The packet switch sends packets from different
data conversations along the best route available in any order. At the
other end the packets are reassembled to form the original message which
is then sent to the receiving computer. Because packets need not be sent
in a particular order, and go any route as long as they reach their destination,
packet switching networks can choose the most efficient route and send
the most efficient number of packets down that route before switching to
A method of transmission in which all bits of a character are sent simultaneously
over separate lines to a high speed printer or other locally attached peripheral.
Contrast with Serial Transmission.
A cross-connect system of mateable connectors that facilitates administration.
PERSONAL COMPUTER (PC)
Computer for personal, single-user use, as opposed to main frames or
mini-computers, which are shared by many users.
An uninterrupted connection between two pieces of equipment.
A functional unit of a node through which data can enter or leave a
A copper foil circuit formed on one or both faces of an insulating board
to which circuit components are soldered. The copper foil pattern serves
to connect components and is produced either by etching or plating.
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).
The time it takes for a signal to travel from one point on a circuit
A specific set of rules, procedures or conventions that two data devices
must accept and use to be able to communicate. Protocols for data transmission
cover such things as framing, error handling, transparency and line control.
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.
A device inserted at intervals along a circuit to boost and amplify
an analog signal being transmitted. Repeaters may also regenerate a digital
signal - squaring it and cleaning it up - but not changing it. Regenerating
the signal removes noise and thus reduces the likelihood of error.
The time it takes a system to react to a given input. The response time
includes the transmission time, the processing time, the time for searching
records and the transmission time back to the originator.
A set of standards specifying various electrical and mechanical characteristics
for interfaces between computers, terminals and modems. The RS232-C standard
was developed by the Electronics Industries Association (EIA), and defines
the mechanical and electrical characteristics for connecting DTE and DCE
data communication devices. It defines what the interface does, circuit
functions and their corresponding connector pin assignments. The standard
applies to both synchronous and asynchronous binary data transmission.
The "Traditional" RS232-C plug has 25 pins. Functionally equivalent to
An EIA recommended standard for cable lengths that extend the RS232-C
50 foot limit and describes the electrical characteristics of balanced-voltage
digital interface circuits.
An EIA recommended standard for cable lengths that extend the RS232-C
50 foot limit and describes the electrical characteristics of unbalanced-voltage
digital interface circuits.
An EIA recommended standard for the mechanical characteristics of two
connectors (a 37 pin connector and a 9 pin connector). Designed for higher
speeds. Not widely used.
A metallic layer, usually in the form of a braid or foil, surrounding one or more electrical conductors to insulate them from electromagnetic interference.
Data transmission over a circuit capable of transmitting in one preassigned
SUBMINIATURE D CONNECTOR
A family of multipin data connectors used in RS232-C communications.
The connectors are available in 9, 15, 25 and 37 pin configurations. Sometimes
referred to as DB9, DB15, DB25 and DB37 connectors respectively.
Transmission in which the data character and bits are transmitted at
a fixed rate with the transmitter and receiver being synchronized. Compare
with Asynchronous Transmission.
A digital transmission link with 1.544 Mbps bandwidth. T1 operates on
two twisted pairs and can handle 24 voice conversations, each digitized
at 64 Kbps. More voice channels are available with advanced digital voice
The AT&T digital transmission system which transmits data at 1.544
1. (Communications) An electrical connection permitting signals to be transmitted onto or off a bus. The link between the bus and the drop cable that connects the workstation to the bus. 2. (Power) An intermediate point in an electric circuit where a connection may be made.
A collective term referring to any DTE that can be connected to a network
node that is capable of sending and receiving data over a data communication
An Ethernet LAN or IEEE 802.3 LAN which uses smaller diameter coaxial
cable than standard Ethernet.
TIME DIVISION MULTIPLEXING (TDM)
A technique for combining many signals on a single circuit by interleaving
bits or bytes of data from successive channels.
A method of computer operation that allows many users to use one computer.
Due to the power and speed of the computer, it appears as though the users
are served simultaneously, when in fact they are being served in sequence.
A threaded connector used to terminate coaxial cables. TNC is an acronym
for threaded Neill-Concelman.
A unique combination of bits used in LANs to grant permission to a station
to transmit. In a ring network, the token circulates continuously; in a
bus it must be addressed.
The geometric description of the physical or logical connections of
a telecommunications system. Typically described as bus, ring or star.
A single device capable of both sending and receiving information.
An abrupt change in voltage, of short duration, which may cause signal
impairments, loss of memory or physical damage to equipment.
Anything such as wire, coaxial cable, fiber optics, air or vacuum, that
is used to carry an electrical signal.
A specialized communications path between two points, one of them usually
being a telephone company central office or switching center.
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.
TWISTED PAIR CABLE
A type of communication transmission cable in which two individually
insulated wires are twisted around each other to reduce induction (thus
interference) from one wire to the other. The pair may be surrounded by
a shield, insulating jacket or additional pairs of wires.
A cable distribution method which uses flat cables placed beneath carpeting
to provide voice, data, video and power services to open office workstations.
VALUE ADDED NETWORK (VAN)
A data communications network leased from a common carrier with extra
equipment, such as an interface computer with a database or storage designed
to provide additional services.
A transmission channel usually limited to the bandwidth of the human
voice (300 - 3000 Hz).
VOICE GRADE LINE
A communications channel which can transmit and receive voice frequencies(300
- 3000 Hz).
The length of an electromagnetic waveform as measured from any point
on one wave to the corresponding point on an adjacent wave, such as from
crest to crest. Wavelength is inversely proportional to frequency.
WIDE AREA NETWORK (WAN)
A communications network designed to serve hundreds or thousands of
miles using common carrier-provided lines, such as the nationwide telephone
A communications channel or medium having a bandwidth sufficient to
carry multiple voice/video or data signals simultaneously.
A CCITT Standard defining the interface specifications between DTE and
DCE for synchronous operation on public data networks, using a 15 pin connector.
A CCITT Standard defining the protocol between DTE and DCE for access to public packet switched networks.
Non-profit organization supported by U.S. industry to establish uniformity
of standards. Members include manufacturers, common carriers and other
standards organizations such as the IEEE. ANSI represents the USA in the
ISO. Compliance with ANSI standards is purely voluntary and, in some respects,
almost identical to existing trade association standards such as NEMA,
SAE, EEI, IEEE, etc. ANSI standards usually form the basis for the general
direction of a UL standard.
BICSI-- Building Industry Consulting Service International
A non-profit, professional organization that promotes the economical
and efficient design and implementation of communications distribution
systems in commercial and multi-family buildings.
CCITT-- Comite Consultatif Internationale de Telegraphique et Telephonique
An international consultative committee that sets international communications
recommendations, which are frequently adopted as standards. Develops interface,
modem and data network recommendations. Private companies, scientific and
trade associations, as well as member nations can participate. CCITT is
part of the International Telecommunications Union (a United Nations Treaty
organization in Geneva).
CSA-- Canadian Standards Association
A testing and certification agency comparable in function to UL and is primarily concerned with the safety of devices, materials and components in the electrical industry.
CSA develops standards of its own for electrical products which parallel
UL standards in many aspects but are not always identical. CSA tests products
and grants paying clients "certification" that their products meet CSA
EIA-- Electronic Industries Association
An USA trade organization that specializes in the development of standards
for the electrical and functional characteristics of interface equipment.
FCC-- Federal Communications Commission
A board of seven commissioners, appointed by the President under the
Communications Act of 1934, having the power to regulate all electrical
communications systems originating in the United States, including radio,
television, facsimile, telegraph, telephone and cable systems.
IEEE-- Institute of Electrical and Electronic Engineers
An international professional engineering society that issues its own
standards and Engineers is a member of ANSI and ISO.
ISO-- International Standards Organization
An international, non-profit standards organization whose membership
standards organizations from participating nations. (ANSI is the USA representative)
NEMA-- National Electrical Manufacturers Association
An US industry association which standardizes specifications for electrical components and power wires and cables.
NEMA is the "voice" of the electrical industry, and through it, standards for electrical products are formulated. Generally these standards promote interchangeability between products of one manufacturer with like products made by another manufacturer.
In some cases, standards relating to product "performance" are also formulated by NEMA but these are the exception rather than the rule. NEMA standards are certainly not compulsory, but generally they are accepted by those manufacturers that help to write them as a way of making their products more saleable and acceptable.
NEMA standards are referenced by many consumers in writing specifications
for the materials they purchase. NEMA standards generally form the basis
for ANSI standards.
TIA-- Telecommunications Industry Association
An USA trade organization that specializes in the development of standards
for telecommunications cabling and its support structures.
UL-- Underwriters Laboratories
A non-profit corporation, operating as a testing facility and developer of safety standards. UL also has the capability for testing to various industry performance specifications such as TIA/EIA, IBM and Bellcore.
By its own definition, Underwriters Laboratories defines itself as follows: "Underwriters Laboratories Inc., founded in 1894, is chartered as a not-for-profit organization without capital stock, under the laws of the state of Delaware, to establish, maintain and operate laboratories for the examination and testing of devices, systems and materials to determine their relation to hazards to life and property."
UL tests products for paying "clients" and if the product submitted passes the requirements of the UL standard for which it is submitted, a UL "listing" or "verification" is granted which allows the manufacturer to use the UL manifest or "label" on its product.
It is important to remember that UL is not an approval agency. It approves nothing, but merely lists a product as meeting its minimum standard for safety or verifies/classifies a product as meeting an industry standard for performance.
Underwriters "Listing" mark on a product is generally accepted by the
public and government agencies as evidence of a "safe" product, not necessarily
a "quality" product.
Top Resources Co., Ltd.
Last Updated at 22-3-1999