Analog - a continuously varying electrical signal in a shape of a wave. It is represented by continuous wave forms that vary in size and number as the source of the information varies. The variations in voice, loudness or pitch that a user hears at the other end reflects differences or fluctuations in the electrical current. Analog is the form of information that comes out of an ordinary voice telephone or from a modem into a telephone line. "People talk" is analog; "computer talk" is digital.

ANSI - American National Standards Institute - ANSI disseminates basic standards like ASCII, and acts as the United States delegate to the ISO -- International Organization for Standardization. ISO is the coordinator of the main networking standards that are put into use today.

Antenna - wires, rods, or other devices used to assist the sending and/or receiving of telecommunications signals.

Asynchronous communication - two-way communication in which there is a time delay between when a message is sent and when it is received (e.g., electronic mail and voice mail). The participants in the communication do not all have to be available at the same time to communicate.

ATM - Asynchronous Transfer Mode - a telecommunications technology, also known as cell switching, which is based on 553-byte cells. In contrast to frame relay which is based on packets of variable length, this fast networking protocol is based on small, uniform packets. Because all ATM cells are exactly alike, the routing equipment that shuttles them around the world can be designed to be extremely fast, and the transmission delays for a series of cells will be relatively constant. ATM communications are suitable for continuous transfer of large amounts of data, including video streams.

Audioconferencing (or Audio-teleconferencing) - two way electronic voice communication between two or more people at two or more locations.

Audiographic teleconferencing - refers to the transmission of graphic and text information over a narrowband telecommunications channel such as a telephone line or a sub-carrier.

Backbone Network - a high speed transmission facility (e.g., optical fiber) designed to interconnect lower speed distribution channels.

Bandwidth - a measure of the information carrying capacity of a communications channel; the higher the bandwidth, the greater the amount of information which can be carried.

Baud - a unit of digital transmission signaling speed of information transmission. It is used to describe the rate of information flow. Given in bits per second (bps) the rate is the highest number of single information elements (bits) transferred between two devices (such as modems or fax machines) in one second.

BBS (Bulletin Board Service) - a computer service that allows remote users to access a central "host" computer to read and post electronic messages.

Bit - stands for binary digit. It is the smallest possible unit of information making up a character or a word in digital code, and is represented as either "on" or "off" by the numbers "0" or "1." An electronic string of bits represents letters and symbols.

BITNET - The acronym for Because It's Time Network, an international electronic network. BITNET, privately owned by a consortium of U.S. colleges and universities, has about 2,500 host computers located primarily at universities.

Bridge - a device which is used to interconnect three or more telecommunications channels such as telephone lines, to permit simultaneous, two-way communication among all points which have been interconnected.

Broadband - communications which are capable of carrying a wide range of frequencies. Broadcast television, cable television, microwave, and satellite are examples of broadband technologies.

Browser - a system that provides access to distributed information located at network-based repositories on the Internet. It enables a user to locate, access, and display information composed of text and still images; to animate moving images; and to play associated sound tracks. Mosaic is an example of a public-domain browser.

Cable television - a transmission system which distributes broadcast television signals and other services by means of coaxial cable. Residential cable subscribers are connected by means of cable to a central community antenna (CATV), which picks up signals from satellites for community distribution.

C-Band - a category of satellite transmission in the 6 GHz range.
C-Band transmission generally requires a large antenna, or "downlink dish" because of its use of longer wavelength frequencies when compared to other transmission systems such as Ku-Band.

CD-ROM Drive - Compact Disk Read-Only Memory - A CD-ROM drive is a read-only, information storage and retrieval device that is commonly used as a computer peripheral (i.e., it is like a computer harddrive, but is able to read information off computer Cds). It can store over 600 megabytes of data -- the equivalent of about 300,000 pages of typewritten text -- and is thus used to handle large databases, to store references such as encyclopedias and for large megabyte software applications. In 1988 the basic standard was extended to include specifications for storing audio, pictures and graphics (CD-ROMXA).

Channel - a radio frequency assignment made according to the frequency band being used and the geographic location of the send/receive sites.

Chat Groups - real-time group communications using computers. Everyone wishing to communicate accesses the same "chat room" provided by an on-line computer service. Messages typed-in by any of the participants are seen by all participants. Special communications software is often needed to participate.

Client - a computer that uses the services of another computer. If the user's computer is a PC or Macintosh and the user dials in to another system, the user's computer becomes a client of the system into which the user dialed.

Client/Server Model - a division of labor between computers. Computers that provide a service other computers can use are known as servers. Servers provide such services as FTP or the World Wide Web. If a user doesn't have these services on her own machine, she can connect to these machines and use these services; her computer thereby becomes a client.

Coaxial cable - a metal cable consisting of a conductor in the form of a tube which can carry broadband signals by guiding high frequency electromagnetic signals. It is used for voice, data, and video.

Common carrier - A telecommunications company that is regulated by government agencies and offers communications relay services to the general public via shared circuits, charging published and non-discriminatory rates.

Compressed video - video images which have been processed to remove redundant information, reducing the amount of bandwidth needed to capture the necessary information so that the information can be sent over narrowband carriers such as a T1 telephone line.

Computer conferencing - group communications through computers, or the use of shared computer files, remote terminal equipment and telecommunications channels for two-way, real-time group communication.

Computer-based training - an educational experience in which all (or almost all) of the instruction is provided via interaction with preproduced learning modules available on a computer or through a computer network. The providing of content and assessment of student progression is programmed into the computer software.

Computer-mediated class or (computer-mediated instruction) - an educational experience in which the computer is used as a major component for providing instructional content and/or used to structure the sequence of student learning.

Computer networking - the use of communications media to connect computers for the purpose of sharing software, sharing computer files, or person-to-person communication.

Conference call - a telephone call which, by making use of a bridge, connects more than two individuals at geographically distinct locations for simultaneous conversation.

Course Credit - a unit of measure used for academic coursework. A course credit in the semester system is three faculty-student contact hours per week over fifteen weeks and in the quarter system is three contact hours per week over ten weeks.

Dedicated line - a telephone line that is reserved for the exclusive use of one customer. It can be used 24 hours a day and usually offers better quality than a standard dial-up telephone line, but may not significantly increase the performance of data communications.

Desktop Videoconferencing - two-way communications of audio and video designed to connect only one or two people per site. Small-scale videoconferencing equipment (compact enough to fit on a desk) or specially-equipped computers are used to communicate.

Digital - discrete signals such as those represented by means of bits (which are either "on" or "off") as opposed to continuously variable analog signals. Used in both electronic and light- based systems, digital signals transmit audio, video, and data as bits. Digital technology allows communications signals to be compressed for more efficient transmission and provides for faster communication with easier error prevention than analog communi- cations. Computers process the bits in the form of bytes. About a half million bytes make a single still picture on a TV screen.

Digital Signal - a form of information transmission in which the signal varies in discrete steps, not in a continuous manner.

Digital Switch - a type of switch in telephone company central offices; it is really a specialized type of computer that tells telephone calls where to go, based on the number "dialed-up" or "touch-toned" by the caller. Compared to previous kinds of switches, digital provides faster, higher quality service and more features for customers.

Digitize - the process by which analog information is converted into digital information. This process is a necessary function for computer imaging applications because visual information is inherently in analog format and most computers use only digital information.

Direct Broadcast Satellite (DBS) - a satellite designed with sufficient power so that inexpensive earth stations, or downlinks, can be used for direct residential reception.

Dish - a parabolic antenna that is the primary element of a satellite earth station, or downlink.

DOS - one of the computer operating systems used for IBM-compatible computers.

Downlink - the path, or link, from the satellite to earth stations which receive its signals. The term is frequently applied to a parabolic antenna that receives signals from a satellite. It is often referred to as: a dish, a terminal, an earth station, or a TVRO (television receive only).

Earth station - the ground equipment, including a dish and other electronics components needed to receive and/or transmit satellite telecommunications signals. An "uplink" is used for sending information to a satellite for distribution to various earth receiving stations, while a "downlink" is used to receive such information.

Electronic bulletin boards - computerized communities usually formed around a common interest or geographic area. Participants in the bulletin board dial-in to join discussion lists on specific topics, share computer files, join chat groups, share announcements, and send/receive e-mail. The bulletin board is usually maintained on a personal computer and is usually accessed by dialing directly to that personal computer.

Electronic query - the ability to use the computer and/or a phone system to obtain information, usually from an electronic source. The query may eventually be passed on to a person.

e-mail - electronic mail - electronic mail is a way to send and receive messages to and from computers. It works by transferring files from one address to another just like regular mail, except the envelope and letter is a computer file.

Encript - to code a message or transmission before it is sent. The code is used to keep the message or transmission from being understood except by those having the key to interpreting the code.

Equal Access - ability to choose between the different long distance carriers. In rural areas, some local exchange carriers are still serviced by only one long distance carrier.

Facsimile (Fax) - a device which electronically transmits and reproduces documents over telephone lines.

Fiber Optics - hair-thin, flexible glass rods encased in cables that use light to transmit audio, video, and data signals.

File Transfer Protocol - (see Protocols)

Frame Relay - a fast networking protocol in which data are packaged in variable-length frames or "envelopes", depending on the size of the packet inside, for shuttling between computer networks. Delays in receiving packets may lead to jumps in a video.

Freenet - a freenet is an open-access, free community computer system offering local community information and limited access to the Internet (e.g., the Cleveland Freenet). A local civic network is a public access network designed to broaden public access to governance, health care and education, and provide the means for citizens to conveniently discharge their public obligations.

Freeze frame - one method of transmitting still images over standard telephone lines. A single image is transmitted every 8-to-30 seconds. This is also referred to as slow scan.

Frequency - the rate at which an electromagnetic signal alternates. It is a term used with analog signals, and is reported in Hertz.

Full-motion video - a standard video signal that can be transmitted by a variety of means including television broadcast, microwave, fiber optics, and satellite. Full-motion video traditionally requires 6 MHz in analog format and 45 Mbps when encoded digitally.

Gateway - a system that interconnects networks (or applications) that communicate using different protocols, and bridges their differences by transforming one protocol into another (i.e., it reformats the data so that it is acceptable for the new network before passing it on).

Gb (Gigabit) - one billion bits of information - usually used to express a data transfer rate (e.g., 1 gigabit/ /second = 1Gbps). The bandwidth of optical fiber is often in the gigabit or billion-bits-per-second range.

Geosynchronous or geostationary orbit - describes the orbit of a satellite whose position relative to the earth's surface is constant so it appears to hover over one spot on the earth's equator.

GHz (Gigahertz) - one billion cycles per second. It is a measurement of analog signal transmission.

Gopher - A system or navigational tool that enables the user to find information on the Internet by using menus. To use Gopher, the user telnets to a Gopher server and begins browsing the menus. The Gopher software was developed by the University of Minnesota for "tunneling" through the Internet.

GUI - Graphical User Interface - a GUI is a display format that uses icons, windows and other graphic elements to execute commands. The Macintosh, Microsoft Windows and OS/2 are GUIs.

HDTV (High Definition Television) - an advanced television system that produces video images as clear as high-quality photography.

Hertz - a unit of frequency equal to one cycle per second.

Hypertext - a system of writing and displaying text that enables the text to contain links to related documents. Hypertext is able to handle graphics and sounds as well as text, and hypermedia documents can thus contain links to other forms of media - sounds, images and movies, as well as to other pieces of text. (In hypertext, selected words in the document are "expanded" -- i.e., linked to other text, file or picture documents.) Hypertext is used in the WWW. _

hypertext markup language (html) - the text composition language that allows a user to compose a document/ /file which may contain text, audio, and still and moving images, and have embedded links to files located on other computing systems.

hypertext transport protocol (http) - the communications protocol used by WWW servers and client systems to identify sources of information and transfer the files containing html-based multimedia objects.

Image Compression - a method to reduce the amount of data needed to reproduce an image.
Lossless image compression means there is no loss of original digital image information upon reconstruction. Lossey compression means that there is some permanent loss of digital image data.

Independent Telephone Company - a local exchange carrier that is not part of the Bell system of operating companies (BOCs). In rural areas, many of the independent telephone companies are cooperatives.

Information Infrastructure - the telecommunication networks, computers, and other end-user devices, software, standards, and skills that collectively enable people to connect to each other and to a vast array of services and information resources.

Interactive video - this term has been used to describe two different technologies: a) the integration of laserdisk or CD-Rom into a computer software program, or b) equipment and networking to provide two-way audio and video communications.

Interconnectivity - the ability of communications networks to connect and communicate with each other. Sometimes special equipment or software is required to connect the networks so capabilities are not lost.

Interoperability - the ability of equipment to work together with a minimal loss in capabilities or requirement for special software or equipment to make the equipment work together.

Internet - the largest international computer network. It is a network of computer networks linking computers from colleges and universities, government agencies, institutions, and commercial organizations worldwide. These networks are able to communicate with each other because they all use the same protocol for sending data (i.e., TCP/IP). Some computers act as gateways connecting the various networks together. Owned by the U.S. government, until recently it was used primarily for research and educational purposes._

Internet Relay Chat - a real-time group communications tool using computers. Everyone wishing to communicate accesses the same "chat room" provided through the internet. Messages typed by any of the participants are seen by all participants. Special communications software is often needed to participate.

Intranet - use of the internet tools for communications aimed at individuals within an organization.

ISDN (Integrated Services Digital Network) - a digital telecommunications channel that allows for the integrated transmission of voice, video, and data; a protocol for high-speed digital transmission. (see Table 2) It uses out-of-band switching (i.e., separate connections carry the switching information). For example, the basic ISDN rate has 2 DS-O channels and a lower capacity channel for the switching signals.

ITFS (Instructional Television Fixed Service) - a non-broadcast television service that is typically used for closed-circuit instructional applications. It requires special antennas and converters to translate signals for viewing.

IXC (Interexchange Carrier) - a telephone company such as AT&T, Sprint, or MCI that carries long distance calls. The IXCs are authorized by the FCC to carry interLATA, interstate traffic and can be authorized by state PUCs to carry interLATA, intrastate traffic. Also known as Long Distance Carriers.

JPEG (Joint Photographic Experts Group) - a standard for compression of static images; it also denotes a graphic file.

Just-in-time learning - the person needing the information can obtain the education or training at a time determined by him/her rather than the educational provider.

Kbs - stands for kilobits (1000 bits) per second. It is a way of reporting the rate of transmission of digital information per second.

Ku-Band - frequencies in the 11-to-14 GHz band used to send and receive signals to and from satellites. Being somewhat more narrow than C-Band transmissions, the dish needed to receive these signals is smaller; Ku-Band tends to be somewhat less expensive than C-Band for this reason.

LANs (Local Area Networks) - data communication networks that are fairly limited in their reach (e.g., the premises of a building or a campus). They are private networks that facilitate the sharing of information and computer resources by the members of a group.

Laser Optical Card - a plastic device the size of a credit card that can hold large amounts of digital data. Typically, the data cannot be altered once they are written to the card.

LATA - Local Access Transport Area - the 161 local telephone service areas created by the divestiture of the regional Bell operating companies (RBOCs), formerly associated with AT&T, in 1984.

LDC (Long Distance Carrier) - see IXC (Interexchange Carrier)

Leased lines - a line rented from a telephone company for the exclusive use of a customer. May also be called a dedicated line.

LEC (Local Exchange Carrier) - a telephone company that carries local calls.

Listserv - a family of programs that automatically manage mailing lists, distributing messages posted to the list, adding and deleting members, without the tedium of someone doing it manually.

Low-Altitude Satellites - satellites that orbit the Earth at lower altitudes than the geosynchronous satellites and cannot maintain a constant position above the Earth. Thus, they are only accessible when they come into view of the receiving dish, two or three times a day for a few minutes at a time.

Mbps - Megabits per second, or one million bits per second.

Microwave - high frequency radio waves used for point-to-point communication of audio, video, and data signals. They can be simplex (omnidirectional) or duplex. The microwave spectrum is generally above 2 GHz. Microwave transmission requires line of sight transmission between sending and receiving antennas.

Modem - a modulator/demodulator. This device converts digital information into analog form for transmission over a telecommunications channel, and reconverts it to digital form at the point of reception.

Mosaic - software that lets you browse the WWW with "point and click" ease. It is one of many WWW browsers. The technology is important to telemedicine because it supports text as well as graphics, sound and movies across the Internet.

MPEG - (Motion Picture Experts Group) - a video compression standard; it also denotes a movie file.

Multiplexer - equipment which transmits two or more lines of voice, data, or video information over a single channel. For example, a multiplexer enables a single T1 telephone line to be split into a number of different "channels" to allow for multiple applications to be carried along the same T1 line.

Multiplexing - the combining of many low-capacity communications channels into one high-capacity communications channel by interleaving the various channels in discrete time or frequency slices.

Narrowband - a telecommunications medium, such as copper wire or part of a coaxial cable channel, that uses (relatively) low frequency signals. Generally speaking, narrowband transmissions go up to 1.544 Mbps.

Network - a set of nodes, points, or locations which are connected by means of data, voice, and video communications for the purpose of exchanging information.

Off-line reader system - a system that allows files or e-mail to be pulled from the internet or other on-line services and to be read on the person's computer. By connecting to the internet only for sending and receiving files, costly connect charges can be avoided.

On-line - information or communications services that are available through the internet or other computer networking services.

On-line multimedia - information available through the internet or other computer networking services that uses more than one communications media (e.g. text, audio, video, animation).

Packet - a bundle of data. On the Internet, data is broken up into small chunks, called packets; each packet traverses the network independently. Packet sizes can vary from roughly 40 to 32,000 bytes, depending on network hardware and media, but packets are normally less than 1500 bytes long.

Packet Switching - the process of transmitting digital information by means of addressed packets - which include data, call control signals, and error control information - so that a channel is occupied only during the transmission of the packet. In contrast, data sent using modems occupies a circuit for the entire duration of the transmission, even when no data is actually traveling over the lines. Using packet switching, the various packets of information can travel along different routes on the network, allowing the carrier to optimize its network capacity.

PACS - Picture Archiving and Communication System - a computer-based system of storing and retrieving radiographic and other images in digital form.

PBX - stands for Private Branch Exchange, a computerized version of the telephone switchboard but with an expanded range of voice and data services. It operates as a private telephone exchange that serves a particular organization and has connections to the public telephone network.

Pixel - Picture Element - the smallest piece of information that can be displayed on a CRT (cathode ray tube) - the monitor or display device. It is represented by a numerical code within the computer and displayed on the monitor as a dot of a specific color or intensity. An image is composed of a large array of pixels of differing intensities or colors. A voxel (volume element) is a three-dimensional version of a pixel. Voxels are generated by computer-based imaging systems, such as CT or MRI. Using voxels, three dimensional simulations of objects can be reconstructed by imaging systems.

Platform - the hardware, memory, and operating system that is installed in a personal computer.

POP (Point of Presence) - The point at which an interexchange carrier's circuits connect with local circuits for transmission and reception of long distance phone calls.

Port - a circuit in an electronic device for the input or output of signals.

Proprietary Standard - a technological standard developed by a single vendor or vendor group. The standard's specifications may be publicized or held confidential.

Protocols - a formal description of message formats and the rules two computers must follow to exchange those messages. Protocols can describe low-level details of machine-to-machine interfaces (e.g., the order in which bits and bytes are sent across a wire) or high-level exchanges between allocation programs (e.g., the way in which two programs transfer a file across the Internet). Standard protocols allow computers from different manufacturers to communicate.

PSTN (Public Switched Telephone Network) - the public telephone network.

Radio technology - used for telecommunications and broadcast services. Used for radio waves in frequencies that are distinct from those assigned to microwave services.

RANs (Rural Area Networks) - as conceptualized by the U.S. Congress, Office of Technology Assessment, RANs would be shared-usage networks, configured to include a wide range of users in rural communities such as educational, health, and business entities.

Receive site - in distance education, a place where a student or students participate in instruction that is originated in a geographically separate location.

RF - stands for radio frequency. Radio frequencies are electromagnetic signals which range from microwave to radio in length.

Routing - The assignment of a communication path by which a telephone call will reach its destination.

Rural Radio Service - the use of certain frequencies, distinct from those in microwave toll service, used to provide wireless telephony in rural areas. It can support the transmission of both analog and digital signals. It provides short-haul telecommunications, and requires different power, transmission, and reception capabilities and devices.

Satellite - an electronics retransmission device serving as a repeater, normally placed in orbit around the earth in geostationary orbit for the purpose of receiving and retransmitting electromagnetic signals. It normally receives signals from a single source and retransmits them over a wide geographic area, known as the satellite's "footprint."

Scanner - A device that acts like a photocopier for a PC. When an article or picture is scanned, the scanner copies it into the computer as an image file.

Send site - in distance education, a place where an instructor originates instruction that is made available to students at sites in geographically separate locations.

Slow scan video - a device that transmits and receives still video pictures over a narrow telecommunications channel, such as standard telephone lines.

Smart Card - a plastic device the size of a credit card with an embedded computer processor and memory.

Standards - standards are agreements on how to implement technologies. Standards for interchanging health data and assigning codes to medical concepts underlie all efforts to make patient records electronically accessible.

Switch - a mechanical or solid state device that opens or closes circuits, changes operating parameters, or selects paths or circuits on a space or time division basis.

Switched Network - a type of system where each user has a unique address (e.g., a phone number) which allows the network to connect any two points directly.

Synchronous - data communications in which transmissions are sent at a fixed rate, with the sending and receiving devices synchronized.

Synchronous Communication - two-way communication in which all participants are available at the same time to communicate. There is no time delay between when a message is sent and when it is received (e.g., a telephone call).

Telecommunications - the use of wire, radio, optical, or other electromagnetic channels to transmit or receive signals for voice, data, and video communications.

Teleconferencing - interactive electronic communication between two or more people at two or more sites which make use of voice, video, and/or data transmission systems: audio, audiographics, computer, and video systems.

Telecourse - an academic course where the primary means of offering instructional content is through the use of prerecorded videotapes that are shown via broadcast or cable television.

Telematics - a term used in Europe to refer to the merger of telecommunication and computer (informatics) technologies

Terrestrial Carrier - a telecommunications transmission system using land-based facilities (microwave towers, telephone lines, coaxial cable, fiber optic cable) as distinguished from satellite transmission.

Transmission Speed - the speed at which information passes over the line; defined in either bits per second (bps) or baud.

Transponder - a microwave repeater (receiver and transmitter) in a satellite that receives signals being sent from earth, amplifies them, and sends them back down to earth for reception purposes. Domestic communication satellites use either 12 or 24 transponders, equivalent to a single channel, which usually have a 36 MHz bandwidth.

Trunk - a large capacity, long distance channel used by common carriers to transfer information between its customers.

Twisted Pair - cable made of a pair of insulated copper wires wrapped around each other to cancel the effects of electrical noise. It can transmit voice and data and, in some cases, low-grade video. It is the most prevalent type of medium in PSTN's local loops. The wire-pair sizes typically range from 19-to-26 gauge. Cables with as many as 2,700 pairs of 26-gauge wire are used in urban areas.

Two-way audio - used in describing a communications technology that features the ability for participants to hear and talk to other participants at any time during the session.

Two-way video - used in describing a communications technology that features the ability to see participants at other sites and they can see you.

Uplink - the path, or link, from a transmitting earth station to the satellite. The term is frequently applied to a transmitting earth station.

URL - Universal Resource Locators - the WWW electronic addressing protocol. It is a way of naming network resources and was originally developed for linking pages together in the World Wide Web.

Virtual - in essence or in effect, but not in fact. The term is often used in referring to a setting or experience that is simulated through the use of technology.

Voice Switching - an electrical technique for opening and closing a circuit, such as changing from one microphone to another microphone or from one video camera to another video camera, in response to the presence or absence of sound.

WAIS - Wide Area Information Servers - a powerful system/software for looking up information in WAIS- indexed databases across the Internet.

WANs (Wide Area Networks) - data communication networks that provide long-haul connectivity among separate networks located in different geographic areas.

WATS (Wide Area Telephone Service) - a flat rate or measured bulk rate long distance service provided on an incoming or outgoing basis. WATS permits a customer, by use of an access line, to make telephone calls to any dialable telephone number in a specific zone for a flat or bulk monthly rate using an 800 number.

Windows environment - a computer or computer software that uses Microsoft Windows or Windows95 for its operating system.

Wireless technologies - communications technologies that utilize radio, microwave or satellite communication channels versus wire, coaxial or optical fiber.

WWW - World Wide Web - an Internet navigation tool (i.e., a hypermedia system for finding and accessing Internet resources). Rather than using menus, the Web uses hypertext links to jump from document to document. The link can be on any computer anywhere in the world. Well-known WWW browsers are Mosaic and Netscape.

Excerpts of this glossary were taken from the Western Cooperative for Educational Telecommunications report TeleHealth 1996: Telemedicine, Distance Education, and Information for Rural Health Care.