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Internet Glossary, Definitions, Telecom Terms, and Resources

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ADSL - See Asymmetric Digital Subscriber Line.

Algorithm - A specific procedure used to modify a signal. For example, the key to a digital compression system is the algorithm that eliminates redundancy.

American National Standards Institute (ANSI) - An official body within the United States delegated with the responsibility of defining standards.

American Standard Code for Information Interchange (ASCII) - Assigns specific letters, numbers, and control codes to the 256 different combinations of 0s and 1s in a byte.

American wire gauge (AWG) - A measurement of wire diameter - the lower the AWG number, the larger the wire diameter. Copper phone wiring usually comes in 24 or 26 AWG.

Analog - A continuously varying signal or wave. As with all waves, analog waves are susceptible to interference which can change the character of the wave.

ANSI - See American National Standards Institute

ASCII - See American Standard Code for Information Interchange.

Asymmetric Digital Subscriber Line (ADSL) - A group of DSL technologies that reserve more bandwidth in one direction than the other, which is advantageous for users that do not need equal bandwidth in both directions. See DSL.

Asynchronous - Occurring at different times. For example, electronic mail is asynchronous communication because it does not require the sender and receiver to be connected at the same time.

Asynchronous Transfer Mode (ATM) - A method of data transportation whereby fixed length packets are sent over a switched network. The ability to ensure reliable delivery of packets at a high rate makes it suitable for carrying voice, video, and data.

Audio On Demand - A type of media that delivers sound programs in their entirety whenever a listener requests the delivery.

AWG - See American Wire Gauge

Backbone - The part of a communications network that handles the major traffic using the highest-speed, and often longest, paths in the network.

Bandwidth - A measure of capacity of communications media. Greater bandwidth allows communication of more information in a given period of time. Bandwidth is generally described either in terms of analog signals in units of Hertz (Hz), which describes the maximum number of cycles per second, or in terms of digital signals in units of bits per second.

Basic Rate ISDN (BRI-ISDN) - The basic rate ISDN interface provides two 64 Kb/s channels (called B channels) to carry voice or data and one 16 Kb/s signaling channel (the D channel) for call information.

Bit - A single unit of data, either a one or a zero, used in digital data communications. When discussing digital data a small "b" refers to bits, and a capital "B" refers to bytes.

Broadband - An adjective used to describe large-capacity networks that are able to carry several services at the same time, such as data, voice, and video.

Broadband Integrated Services Digital Network (BISDN) - A second-generation ISDN technology that uses fiber optics for a network that can transmit data at speeds of 155 megabits per second and higher.

BISDN - See broadband integrated services digital network.

Byte - A compilation of bits, seven bits in accordance with ASCII standards and eight bits in accordance with EBCDIC standards.

CAP - See Carrierless Amplitude Phase

Carrier - an electromagnetic wave or alternating current which is modulated to carry signals in radio, telephonic, or telegraphic transmission.

Carrierless Amplitude Phase (CAP) - A type of quadrature amplitude modulation, used for some types of DSL, that stores pieces of a modulated message signal in memory and then reassembles the parts in the modulated wave.

Central Office (CO) - A telephone company facility that handles the switching of telephone calls on the public switched telephone network (PSTN) for a small regional area.

Central Processing Unit (CPU) - The "brains" of a computer, which uses a stored program to manipulate information.

Circuit-Switched Network - A type of network in which a continuous link is established between a source and a receiver. Circuit switching is used for voice and video to ensure that individual parts of a signal are received in the correct order by the destination site.

CO - See central office

Common Carrier - A business, including telephone and railroads, which is required by law to provide service to any paying customer on a first-come, first-serve basis.

Competitive Local Exchange Carrier (CLEC) - An American term for a telephone company that was created after the Telecommunications Act of 1996 made it legal for companies to compete with the ILECs. Contrast with ILEC.

CLEC - See competitive local exchange carrier.

Compression - The process of reducing the amount of information necessary to transmit a specific audio, video, or data signal. core network - The combination of telephone switching offices and transmission plant connecting switching offices together. In the U.S. local exchange network, core networks are linked by several competing Interexchange networks; in the rest of the world the core network extends to national boundaries.

CPE - See customer premises equipment.

CPU - See central processing unit.

Crosstalk - Interference from an adjacent channel.

Customer Premises Equipment (CPE) - Any piece of equipment in a communication system that resides within the home or office. Examples include modems, television set-top boxes, telephones and televisions.




DBS - See direct broadcast satellite.

Dedicated Connection - A communication link that operates constantly.

Dial-Up Connection - A data communication link that is established when the communication equipment dials a phone number and negotiates a connection with the equipment on the other end of the link.

Digital Signal - A signal that takes on only two values, off or on, typically represented by "0" or "1." Digital signals require less power but (typically) more bandwidth than analog, and copies of digital signals can be made exactly like the original.

Digital Subscriber Line (DSL) - A data communications technology that transmits information over the copper wires that make up the local loop of the public switched telephone network (See local loop).) It bypasses the circuit-switched lines that make up that network and yields much faster data transmission rates than analog modem technologies

Digital Subscriber Line Access Multiplexor (DSLAM) - A device found in telephone company central offices that takes a number of DSL subscriber lines and concentrates these onto a single ATM line.

Direct Broadcast Satellite (DBS) - A broadcast technology that uses satellites orbiting the Earth to broadcast television or data signals to an 18" dish antenna.

Discrete Multi-Tone Modulation (DMT) - A method of transmitting data on copper phone wires that divides the available frequency range into 256 sub-channels or tones, and which is used for some types of DSL.

Discrete Wavelet Multitone (DWMT) - A variation of DMT modulation that improves performance by using wavelets rather than tones to provide additional isolation of sub-channels.

DMT - See discrete multi-tone modulation.

DNS - See domain name system. domain name system (DNS) - The protocol used for assigning text addresses (such as for specific computers and computer accounts on the Internet.

DSLAM - See digital subscriber line access multiplexor.

DWMT - See discrete wavelet multitone.

E-1 - A dedicated digital communication link provided by a European telephone company that offers 2.048 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers

Echo Cancellation - The elimination of reflected signals ("echoes") in a two-way transmission created by some types of telephone equipment, used in data transmission to improve the bandwidth of the line.

FDM - See frequency division multiplexing. fiber optics. Thin strands of ultrapure glass or plastic that can be used to carry light waves from one location to another.

Fiber-to-the-Cabinet (FTTCab) - network architecture where an optical fiber connects the telephone switch to a street-side cabinet where the signal is converted to feed the subscriber over a twisted copper pair.

Fiber-to-the-Curb (FTTC) - The deployment of fiber optic cable from a central office to a platform serving numerous homes. The home is linked to this platform with coaxial cable or twisted pair (copper wire). Each fiber carries signals for more than one residence, lowering the cost of installing the network versus fiber to the home.

Fiber-to-the-Home (FTTH) - The deployment of fiber optic cable from a central office to an individual home. This is the most expensive broadband network design, with every home needing a separate fiber optic cable to link it with the central office.

Frame Relay - A high-speed packet switching protocol used in wide area networks (WANs), often to connect local area networks (LANs) to each other, with a maximum bandwidth of 44.725 megabits per second.

Frequency - The number of oscillations in an alternating current that occur within one second, measured in Hertz (Hz).

Frequency Division Multiplexing (FDM) - The transmission of multiple signals simultaneously over a single transmission path by dividing the available bandwidth into multiple channels that each cover a different range of frequencies.

FTTC - See fiber-to-the-curb.

FTTH - See fiber-to-the-home.

Full-Motion Video - The projection of 20 or more frames (or still images) per second to give the eye the perception of movement. Broadcast video in the United States uses 30 frames per second, and most film technologies use 24 frames per second.

G.dmt - A kind of asymmetric DSL technology, based on DMT modulation, that offers up to 8 megabits per second downstream bandwidth, 1.544 Megabits per second upstream bandwidth. "G.dmt" is actually a nickname for the standard officially known as ITU-T Recommendation G.992.1. (See International Telecommunications Union.)

G.lite [pronounced "G-dot-light"] - A kind of asymmetric DSL technology, based on DMT modulation, that offers up to 1.5 megabits per second downstream bandwidth, 384 Kilobits per second upstream, does not usually require a splitter and is easier to install than other types of DSL. "G.lite" is a nickname for the standard officially known as G.992.2. (See International Telecommunications Union.)

G.992.1 - See G.dmt.

G992.2 - See G.lite.

General Switched Telephone Network (GSTN) - See public switched telephone network.

Gigabyte - 1,000,000,000 bytes, or 1,000 megabytes (see Byte).

Graphical User Interface (GUI) - A computer operating system that is based upon icons and visual relationships rather than text. Windows and the Macintosh computer use GUIs because they are more user friendly.

GSTN - See general switched telephone network.

GUI - See graphical user interface.

HDSL - See high bit rate digital subscriber line.

Hertz - See frequency.

Hybrid Fiber/Coax (HFC) - A type of network that includes coaxial cables to distribute signals to a group of individual locations (typically 500 or more), and a fiber optic backbone to connect these groups.

High Bit Rate Digital Subscriber Line (HDSL) - A symmetric DSL technology that provides a maximum bandwidth of 1.5 megabits per second in each direction over two phone lines, or 2 Megabits per second over three phone lines.

High Bit Rate Digital Subscriber Line II (HDSL II) - A descendant of HDSL which offers the same performance over a single phone line.

high-definition television (HDTV) - Any television system that provides a significant improvement in picture quality over existing television systems. Most HDTV systems offer more than 1,000 scan lines, in a wider aspect ratio, with superior color and sound fidelity.

HTML - See hypertext markup language.

HTTP - See hypertext transfer protocol.

hypertext - Documents or other information with embedded links that enable a reader to access tangential information at specific points in the text.

hypertext markup language (HTML) - The computer language used to create hypertext documents, allowing connections from one document or Internet page to numerous others. HTML is the primary language used to create pages on the World Wide Web.

hypertext transfer protocol (HTTP) - The first part of an address (URL) of a site on the Internet, signifying a document written in Hypertext Markup Language (HTML).

Hz - See frequency.

IDSL - See ISDN digital subscriber line.

IEEE - See Institute of Electrical and Electronics Engineers.

ILEC - See incumbent local exchange carrier.

incumbent Local Exchange Carrier (ILEC) - A large telephone company that has been providing local telephone service in the United States since the divestiture of the AT&T telephone monopoly in 1982.

Institute of Electrical and Electronics Engineers (IEEE) - A membership organization comprised of engineers, scientists and students that sets standards for computers and communications.

Integrated Services Digital Network (ISDN) - A circuit-switched communication network, closely associated with the public switched telephone network, that allows dial-up digital communication at speeds up to 128 kilobits per second.

Inter-Exchange Carrier (IXC) - A long-distance telephone carrier.

International Organization of Standardization (ISO) - Develops, coordinates, and promulgates international standards that facilitate world trade.

International Telecommunication Union (ITU) - A United Nations organization that coordinates use of the electromagnetic spectrum and creation of technical standards for telecommunication and radio communication equipment.

International Telecommunication Union/Telecommunication Standardization Sector (ITU-T) - The branch of the ITU that is responsible for telecommunication standardization.

Internet Engineering Task Force (IETF) - The standards organization that standardizes most Internet communication protocols, including Internet protocol (IP) and hypertext transfer protocol (HTTP).

IETF - See Internet Engineering Task Force.

Internet protocol (IP) - The standard signaling method used for all communication over the Internet

Internet service provider (ISP) - An organization offering and providing Internet access to the public using computer servers connected directly to the Internet.

Intranet - A network serving a single organization or site that is modeled after the Internet, allowing users access to almost any information available on the network. Unlike the Internet, intranets are typically limited to one organization or one site, with little or no access to outside users.

IP - See Internet protocol

ISDN - See integrated services digital network.

ISDN digital subscriber line (IDSL) - A type of DSL that uses ISDN transmission technology to deliver data at 128kbps into an IDSL "modem bank" connected to a router.

ISO - See International Organization of Standardization.

ISP - See Internet service provider.

ITU - See International Telecommunication Union.

ITU-T - See International Telecommunication Union/Telecommunication Standardization Sector.

IXC - See Inter-exchange carrier.

Joint Photographic Experts Group (JPEG) - A committee formed by the International Organization of Standardization to set standards for digital compression of still images. Also refers to the digital compression standard for still images created by this group.

JPEG - See Joint Photographic Experts Group.

Kilobit - One thousand bits (see bit).

Kilobyte - One thousand bytes (see byte).

Laser - From the acronym for "Light Amplification by Stimulated Emission of Radiation." A laser usually consists of a light-amplifying medium placed between two mirrors. Light not perfectly aligned with the mirrors escapes out the sides, but light perfectly aligned will be amplified. One mirror is made partially transparent. The result is an amplified beam of light that emerges through the partially transparent mirror.

Last Mile - See local loop.

Local Access Transport Area (LATA) - The geographical areas defining local telephone service. Any call within a LATA is handled by the local telephone company, but calls between LATAs must be handled by long-distance companies, even if the same local telephone company provides service in both LATAs.

LATA - See local access transport area.

Local Area Network (LAN) - A network connecting a number of computers to each other or to a central server so that the computers can share programs and files.

LAN - See local area network.

Local exchange carrier (LEC) - A local telephone company. LECs provide telephone service for phone calls originating and terminating within a single LATA.

Local Loop - The copper lines between a customer's premises and a telephone company's central office (See central office).

Mb/s - Megabits per second.

Megabit - One million bits.

Megabyte - 1,000,000 bytes, or 1,000 kilobytes (see Byte).

Millions of instructions per second (MIPS) - This is a common measure of the speed of a computer processor.

Modem (MOdulator-DEModulator) - A device that converts digital data into analog signals and vice-versa for transmission over a telephone line.

Moving Pictures Experts Group (MPEG) - A committee formed by the ISO to set standards for digital compression of full-motion video. Also stands for the digital compression standard created by this committee.

MPEG-1 - An international standard for the digital compression of VHS-quality, full-motion video.

MPEG-2 - An international standard for the digital compression of broadcast-quality, full-motion video.

MPEG-3 - An international standard for the digital compression of broadcast-quality, audio.

Multicast - The transmission of information over the Internet to two or more users at the same time.

Multiplexing - Transmitting multiple signals over a single communications line or computer channel. The two common multiplexing techniques are frequency division multiplexing, which separates signals by modulating the data onto different carrier frequencies, and time division multiplexing, which separates signals by interleaving bits one after the other.

NAP - See network access provider.

Narrowband - A designation of bandwidth less than 56 kilobits per second.

Narrowband ISDN - same as ISDN.

Network Access Provider (NAP) - Another name for a provider of networked telephone and associated services, usually in the U.S.

Network Service Provider (NSP) - A high-level Internet provider that offers high-speed backbone services.

Network Termination Equipment (NTE) - The equipment at the ends of the communication path.

N-ISDN - See narrowband ISDN.

NSP - See network service provider.

NTE - See network termination equipment.

OC-3 - See optical carrier 3.

ONU - See optical network unit.

Optical Carrier 3 (OC-3) - An fiber optic line carrying 155 megabits per second; a U.S. designation generally recognized throughout the telecommunications community worldwide.

Optical Network Unit (ONU) - A form of access node that converts optical signals transmitted via fiber to electrical signals that can be transmitted via coaxial cable or twisted pair copper wiring to individual subscribers. (See hybrid fiber/coax.)

Packet-Switched Network - A network that allows a message to be broken into small "packets" of data that are sent separately by a source to the destination. The packets may travel different paths and arrive at different times, with the destination sites reassembling them into the original message. Packet switching is used in most computer networks because it allows a very large amount of information to be transmitted through a limited bandwidth.




Passive optical network (PON) - a fiber-based transmission network containing no active electronics.

Peripheral - An external device that increases the capabilities of a communication system.

Plain Old Telephone Service (POTS) - An acronym identifying the traditional function of a telephone network to allow voice communication between two people across a distance. In most contexts, POTS is synonymous with the public switched telephone network (PSTN).

Point of Presence (POP) - The physical point of connection between a data network and a telephone network.

PON - See passive optical network.

POP - See point of presence.

Postal, Telegraph and Telephone (PTT) - The generic European name usually used to refer to state-owned telephone companies.

POTS - See plain old telephone service.

POTS splitter - A device that uses filters to separate voice from data signals when they are to be carried on the same phone line, required for several types of DSL service.

PRI-ISDN - See primary-rate ISDN.

Primary-Rate ISDN (PRI-ISDN) - The primary rate ISDN interface provides 23 64 Kb/s channels (called B channels) to carry voice or data and one 16 Kb/s signaling channel (the D channel) for call information.

PTT - See Postal, Telegraph and Telephone. public switched telephone network (PSTN) - The worldwide communications network that carries phone calls and data.



Radio Frequency (RF) - Electromagnetic carrier waves upon which audio, video, or data signals can be superimposed for transmission.

RADSL - See rate-adaptive asymmetric digital subscriber line.

Rate-Adaptive Digital Subscriber Line (RADSL) - A variation of DSL that uses carrierless amplitude phase modulation, divides the available frequencies into discrete sub-channels and also maximizes performance by adjusting the transmission to the quality of the phone line while in use.

RBOC - See Regional Bell Operating Company.

Regional Bell Operating Company (RBOC) - One of the seven local telephone companies formed upon the divestiture of AT&T in 1984. The seven are: NYNEX, Bell Atlantic, BellSouth, Southwestern Bell, U S WEST, Ameritech, and Pacific Telesis.

RF - See radio frequency.

Router - The central switching device in a packet-switched computer network that directs and controls the flow of data through the network.


SCSI - See small computer system interface.

Small Computer System Interface (SCSI) [pronounced "scuzzy"] - A type of interface between computers and peripherals that allows faster communication than most other interface standards, often used to connect PCs to external disk drives.

SDSL - Symmetric Digital Subscriber Line - This technology provides the same bandwidth in both directions, upstream and downstream. That means whether you're uploading or downloading information, you have the same high-quality performance. SDSL provides transmission speeds within a T1/E1 range, of up to 1.5 Mbps at a maximum range of 12,000 - 18,000 feet from a central office, over a single-pair copper wire. This option is ideal for small and medium sized businesses that have an equal need to download and upload data over the Internet.




T1.413 - The American National Standards Institute (ANSI) standard for asymmetric digital subscriber line using discrete multitone modulation, which the G.dmt standard is based on.

T-1 - Also known as DS1 and T1, a T-1 is dedicated digital communication link provided by a telephone company that offers 1.544 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers.

T-3 - Also known as DS3 and T3, a T-3 is a dedicated digital communication link provided by a telephone company that offers 44.75 megabits per second of bandwidth, commonly used for carrying traffic to and from private business networks and Internet service providers.

TCP/IP - See transmission control protocol/Internet protocol.

Telecommuting - The practice of using telecommunication technologies to facilitate work at a site away from the traditional office location and environment. teleconference - Interactive, electronic communication among three or more people at two or more sites. Includes audio-only, audio and graphics, and video-conferencing.

Terabyte - 1,000,000,000,000 bytes, or 1,000 gigabytes (see Byte).

Time Division Multiplexing (TDM) - A digital data transmission method that takes signals from multiple sources, divides them into pieces which are then placed periodically into time slots, transmits them down a single path and reassembles the time slots back into multiple signals on the remote end of the transmission.

Transmission Control Protocol/Internet Protocol (TCP/IP) - A method of packet-switched data transmission used on the Internet. The protocol specifies the manner in which a signal is divided into parts, as well as the manner in which "address" information is added to each packet to ensure that it reaches its destination and can be reassembled into the original message.

Twisted Pair - The set of two copper wires used to connect a telephone customer with a switching office, loosely wrapped around each other to minimize interference from other twisted pairs in the same bundle. Synonymous with 2-wire line.


UAWG - See Universal ADSL Working Group.

Uniform Resource Locator (URL) - A text-based address used to identify specific resources on the Internet, such as web pages. URLs are arranged in a hierarchical form that specifies the name of the server on which a resource is located (such as and the name of the file on that server (

Universal ADSL Working Group (UAWG) - An organization composed of leading personal computer industry, networking and telecommunications companies with the goal of creating an interoperable, consumer-friendly ADSL standard titled the G.992.2 standard, and commonly referred to as the G.lite standard.

Universal Serial Bus (USB) - A computer interface with a maximum bandwidth of 1.5 Megabytes per second used for connecting computer peripherals such as printers, keyboards and scanners.

Universal Service Provider (USP) - A company that sells access to phone, data, and entertainment services and networks.

URL - See Uniform Resource Locator.

USB - See Universal Serial Bus.

USP - See universal service provider.


Variable Bit Rate (VBR) - A data transmission that can be represented by an irregular grouping of bits or cell payloads followed by unused bits or cell payloads.

VDSL - See very high bit rate digital subscriber line. very high bit rate digital subscriber line (VDSL) - An asymmetric DSL that delivers from 13 to 52 megabits per second downstream bandwidth and 1.5 to 2.3 megabits per second upstream.

Video on Demand (VOD) - A pay-per-view television service in which a viewer can order a program from a menu and have it delivered instantly to the television set, typically with the ability to pause, rewind, etc.

Video Conference - Interactive, audiovisual communication among three or more people at two or more sites.

Virtual Reality Markup Language (VRML) - A computer language that provides a three-dimensional environment for traditional Internet browsers, resulting in a simple form of virtual reality available over the Internet.

VOD - See video on demand.

VRML - See virtual reality markup language.

WAN - See wide area network.

Wide Area Network (WAN) - A network that interconnects geographically-distributed computers or LANs.

X.25 Data Protocol - A packet switching standard developed in the mid-1970s for transmission of data over twisted pair copper wire.

xDSL - See DSL.


* Glossary published with the permission of Dr. Augie Grant, author of "Communication Technology Update (Ninth Edition)"

Dr. Grant is an Associate Professer in the College of Mass Communications and Information Studies University of South Carolina Columbia, SC 29208

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