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Bandwidth: A measure of the information-carrying capacity of a communications channel. The speed (bit rate or velocity) at which data can be transferred and presented.

Baud: Speed of transmission in bits per second (b.p.s.) in binary (two-state) telecommunications transmission.

Bell operating company (B.O.C.): One of the 22 regulated local-exchange carriers divested from the a.t.&t. Bell telephone system by the Modification of Final Judgment (see related story ) in 1984. The 22 companies are organized into subsidiaries of the seven regional holding companies, which are also called regional Bell operating companies.

Binary: A numbering system having only two digits, typically 0 and 1.

Broadband: Any system able to deliver multiple channels and/or services to its users or subscribers. Generally refers to cable-television systems. Sometimes called wideband.

Broadband communications: Term characterizing both digital and analog transmission systems. Broadband communications is generally understood to indicate either a fast data-rate digital system or a wide bandwidth analog system.

Cable television system (CATV): A broadband communications system capable of delivering multiple channels of programming from a set of centralized satellite and off-air antennae, generally by coaxial cable, to a community. Many cable-television designs integrate fiber-optic and microwave links.

CD-ROM: An acronym for "compact disk-read only memory." An optical-storage device, identical to those used to record music, that holds roughly 600 times as much data--including text, graphics, sound, and video--as a standard computer floppy disk.

Coaxial cable: A type of cable used for broadband data and cable systems. Also known as "coax."

Common carrier: A telecommunications company that offers communications services to the general public via shared circuits at published tariff rates. In the United States, the Federal Communications Commission or various state public-utility commissions regulate common carriers.

Consortium for School Networking (CoSN):

A nonprofit organization of K-12 educators, hardware and software vendors, and Internet providers. CoSN has worked to inform teachers and parents about the Internet (see next page) and its potential as an instructional tool.

Database: Information or files stored in a computer for subsequent retrieval and use.

Digital: A function that operates in discrete steps as contrasted with a continuous, or analog, function. Digital computers manipulate numbers encoded in binary (on-off) forms, while analog computers sum continuously varying forms. Digital communications is the transmission of information using discontinuous, discrete electrical or electromagnetic signals that change in frequency, polarity, or amplitude. Analog forms may be encoded for transmission on digital communications systems.

Direct broadcast satellite (D.B.S.): A satellite system designed with sufficient power so that inexpensive earth stations can be used to receive signals.

Download: To transfer information from a computer network to a personal computer.

(See ducational Resources Information Center (ERIC): A clearinghouse of information for educators, supported by the U.S. Education Department. It operates AskERIC, an Internet site with on-line resources for K-12 teachers.

Electronic mail ("e-mail"): The delivery of correspondence, including graphics, by electronic means, usually by interconnecting computers, word processors, or facsimile equipment.

Fax: Facsimile; a system for the transmission of images. A black-and-white reproduction of a document or picture transmitted over a telephone or other transmission system.

Federal Communications Commission: A board of five members (commissioners) appointed by the President and confirmed by the U.S. Senate under the provision of the Communications Act of 1934. The F.C.C. has the power to regulate interstate communications.

Fiber-optic cable: A cable containing one or more optical fibers.

Fiber optics: The technology of guiding and projecting light for use as a communications medium. Hair-thin glass fibers that allow light beams to be bent and reflected with low levels of loss and interference are known as "glass optical wave guides" or simply "optical fibers."

Geostationary satellite: A communications satellite, with a circular orbit 22,400 miles in space. The satellite is stationary when viewed from the Earth.

Hardware: The electrical and mechanical equipment used in telecommunications and computer systems. Contrasted with software, the programs and files that run in the equipment.

Headend: The control center of a cable-television system, where incoming signals are amplified, converted, processed, and combined into a common cable for transmission to subscribers.

Hypermedia: A nonlinear way of presenting information that allows users to access related works or images from a single computer screen. For example, a user reading an encyclopedia entry on jazz could also hear excerpts from recordings, read biographies of jazz artists, and view photos of them. Apple Computer Inc.'s HyperCard is the best-known example of hypermedia. Presumably, this type of interface is similar to normal human cognitive processes. Also known as "hypertext."

Information utility: A term increasingly used to refer to services that offer a wide variety of information, communications, and computing services to subscribers; examples include the Source, CompuServe, and Dow Jones News Retrieval.

Integrated services digital network (i.s.d.n.): A public switched network (see below) providing digital connections for the concurrent transmission of voice, video, data, and images. Often seen as a technological bridge between the current telephone system and an upgraded, broadband network.

Interactive media: New telecommunications systems designed to permit two-way communications between televisions or computers in one location with software stored on a central computer. Can also allow individuals in distant locations to communicate, teach, or learn from one another.

Interactive television (ITV): Two-way communications using a television as the display. Uses include entertainment, information retrieval, education, and shopping.

Internet: A widely used public computer network, initially developed by the U.S. military, that links smaller computer networks and allows users on different electronic-mail systems to communicate with one another on a global scale.

Local access and transport area (LATA): A telephone service region incorporating local exchanges, usually smaller than a state.

Local area network (LAN): A special linkage of computers or other communications devices into their own network for use by an individual or organization, such as a schoolwide network.

Local exchange carrier (L.E.C.): A telephone company that provides service in the local (that is, "exchange") area as well as access to other carriers.

Modem: Short for "modulator-demodulator." The equipment used to link a computer to a telephone line.

Modification of Final Judgment (M.F.J.): A 1982 agreement between A.T.&T. and the U.S. Justice Department that settled an antitrust case filed in 1974. The M.F.J. caused the divestiture or breakup of the Bell system.

National Information Infrastructure (N.I.I.): A broad proposal for the federal government to establish standards and governing bodies for the transmission of digital data. Most provisions of the N.I.I. are still being debated.

National Telecommunications and Information Administration (N.T.I.A.): An office of the U.S. Commerce Department that is designated to provide "seed grants" to support experimental educational and other public-benefit uses of the N.I.I.

Network: The circuits over which computers or other devices are connected with one another, such as over a telephone network.

On-line: Being actively connected to a network or computer system; usually being able interactively to exchange data, commands, and information.

Open-network architecture: An industrywide standard that allows different telecommunications vendors to interconnect with a network.

Public switched telephone network: The formal name given to the commercial telephone business in the United States; includes all the operating companies.

Public Utility Commission: The body, usually a state entity, that sets telephone rates.

Switched video: A residential and business video service in which customers can dial up others (much like today's telephone service) and through which customers can order video-on-demand and other video-based services. Sometimes called video dial tone.

Tariff: The published rate for a service, equipment, or facility established by the communications common carrier.

Telecommuting: The use of computers and telecommunications to enable people to work at home. More broadly, the substitution of telecommunications for transportation.

Teleconference: The simultaneous visual and/or sound interconnection that allows individuals in two or more locations to see and talk to one another in a long-distance conference arrangement.

Twisted pair: The term given to the wires that connect local telephone circuits to the central telephone office.

Two-way cable: In cable television, a distribution system that has been designed to support normal "downstream" transmissions (from the cable headend to customers), as well as "upstream" transmissions (from customer locations to the headend). Two-way cable systems are not necessarily interactive cable systems.

Universal service: Traditionally defined as making affordable voice telephone service easily available. In the coming years, it could be broadened to include other telecommunications services.

Upload: To transfer information from a personal computer into a computer network, where others can use it.

Very small aperture terminal (V.S.A.T.): A special satellite dish especially valuable for networking businesses.

Wide-area network: A network of computers spread out over a large geographic area (compare with local area network). Florida, Kentucky, Pennsylvania, Texas, and Virginia have developed, or are developing, statewide computer networks dedicated to educational use.

Worldwide Web: An Internet service that lets users retrieve hypertext and graphics from various sites. Often called just "the Web," it has become one of the most popular Internet services over the past two years.

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