0-9

10BaseT
A form of Ethernet and IEEE (Institute of Electrical and Electronic Engineers and a set of standards for the telecommunications industry) 802.3 network cabling using thick coax. It refers to 10Mbps-speed, baseband-transmission, twisted-pair cable with a maximum segment length of 100m.

100BaseT
IEEE (Institute of Electrical and Electronic Engineers) standard from proposals by the Fast Ethernet Alliance (including 3Com and SynOptics). It will support Category 3,4 & 5 UTP cabling. It refers to 100Mbps-speed, baseband-transmission, twisted-pair cable with a maximum segment length of 100m.

access charges
Fees paid by long-distance carriers to local telephone companies for use of local facilities to originate or terminate calls.

access method
Technique for moving data between main storage and input/output devices. In a Systems Network Architecture (SNA) environment, it is the software that controls the flow of information in a network.

American National Standards Institute (ANSI)
ANSI is responsible for the establishment of many standards, including a number of data communications and terminal standards.

American Standard Code for Information Interchange (ASCII)
The 7-bit code, intended as a U.S. standard for the interchange of information among communications devices.

analog
An analog (U.S. analog) signal is electrical and varies constantly in voltage, unlike a digital signal which varies between two constant values, usually denoted as 0 and 1. The value of the analog signal varies all the time during transmission, whereas a digital signal changes only between two set values without intermediate variations.

AppleTalk
A seven-layer protocol stack developed by Apple for communications among its Apple Macintosh product range. Apple defines it in similar terms to the functionality of the seven-layer OSI (Open Systems Interconnection) model.

Asymmetric
The transmission of data in which the receiving (downstream) and sending (upstream) bandwidths are different.

Asymmetrical Digital Subscriber Line (DSL)
An emerging service for transmitting information at 128,000 bits per second (128Kbps) and receiving up to 7 megabits per second (7Mbps) over standard copper telephone lines. Various speeds are being introduced.

asynchronous
Type of transmission in which each character is transmitted independently without reference to a standard clock.

Asynchronous Transfer Mode (ATM)
A cell-based data-transfer technique in which channel demand determines packet allocation. ATM offers fast packet technology and real-time, demand-led switching for efficient use of network resources. It is also the generic term adopted by ANSI (American National Standards Institute) and the ITU-TS (International Telecommunication Union-Telecommunication Standardization Sector) to classify cell relay technology within the realm of broadband WANs, specifically B-ISDN. In ATM, units of data are not time related to each other and, as part of the B-ISDN standard, are specified for digital transmission speeds from 34Mbps to 622Mbps. IBM currently offers ATM at a non-standard 25Mbps format.

backbone
The main conduit of a computer network, to which all other users and networks connect. For example, the Arpanet, and later the NSFNet, once served as a backbone for the Internet, but now there are many others.

bandwidth
(1) Difference between the top and bottom limiting frequencies of a continuous frequency band. (2) Indicates the information-carrying capacity of a particular channel. Digital transmission capacity is expressed in bps, or Mbps. Fiber optic bandwidth is often expressed as the capacity to transmit information within a specific time period for a specific length (i.e. 12Mbps/km).

Base Line Service
Service available to Business End-Users, providing a direct connection to a long distance carrier (IXC). This service is also referred to as "bypass" service. Ultimately, Base Line Service gives the Business End-User a better price on telecommunication services. The Business End-User is the direct customer of the provider.

baseband
A term defining any network in which the information is modulated onto a single frequency. The digital input is applied directly to the transmission media without the intervention of a modulating device, which works well if there is wide bandwidth and distances no more than several hundred meters are involved. It is common in LANs and limited distance modems. All stations attached to the network have to participate in every transmission. Baseband is simpler and cheaper than broadband, and it permits only one "conversation" at a time because the whole of the bandwidth is used to transmit a single digital signal. Ethernet is a baseband network.

basic input/output system (BIOS)
A set of programs, usually in firmware, that establishes each computer's central processing unit to communicate with printers, disks, keyboards, consoles, and other attached input and output devices.

basic rate (BRI)
A service in ISDN that provides each user with two 64Kbps bearer (or B) channels for message information and one 16 Kbps (or D) channel for signaling and control over an existing telephone line. It is also referred to as 2B=D.bps bits per second.

Basic Rate Access
Two 64Kbps "B" channels + one 16Kbps "D" channel (2B + D), carrying user traffic and signaling information respectively to the user via twisted-pair local loop.

bearer channel
A 64Kbps channel in Basic Rate and Primary Rate services of ISDN used for customer message exchange.

B-ISDN (Broadband ISDN)
The proposed advanced version of ISDN, providing speeds of 155.52Mbps and higher. Standards of switching technology that will work this fast are under development. It promises universal coverage based on ATM/SDH (Synchronous Digital Hierarchy, i.e. ITU-T) technologies and optical fiber, supporting data, voice, and video traffic.

bit See also: byte
A binary unit of information that can have two values: 0 or 1. The word comes from a contraction of binary digit.

broadband
(1) Sometimes referred to as wideband, it describes any network that multiplexes multiple, independent network carrier frequencies onto a single cable. It allows multiple simultaneous "conversations," because the independent networks operate on different frequencies and do not interfere with each other. (2) In LAN terminology, it refers to a system in which multiple channels access a medium; for example, coaxial cable to carry multiple separate LANs whose transmission is being modulated at different frequencies. (3) In cable television, broadband describes the ability to carry 30 or more TV channels and is synonymous with wideband. (4) In Telecommunications, broadband is any data transmission with relative size equal to or greater than 256 kilobits per second.

browser
Software that lets you travel the World Wide Web. (i.e. Internet Explorer)

bus topology
A type of network in which all tie devices are connected in a line to a single cable. A bus network has two distinct ends. All devices attached to a bus network have equal access to it and can see all the messages that are put onto the network. Each device determines which messages are intended for it alone, and selects those.

byte
(1) Representation of a character. (2) Group of eight bits. Typically, a 16-bit "word" is itself divided into two bytes for handling. (3) Unit of measurement used to rate storage capacity of disks; usually the smallest addressable unit of information in a data store or memory. One thousand bytes is a kilobyte; one million bytes is a megabyte.

cable modem See also: modem
A modem that uses coaxial cable to connect to the Internet rather than regular phone lines or ISDN lines.

cache
High-speed memory section that holds blocks of data on which the CPU is currently working; designed to minimize the time that the CPU spends accessing memory.

Category 5 (CAT 5)
Cabling standard specified by EIA/TIA (Electronic Industries Association/Telecommunications Industry Association) 568 for use at speeds up to 100Mbps, including FDDI, 100BaseT and 100BaseVG-AnyLan, and potentially ATM at 155Mbps.

central office
A local telephone company wiring office and switching center where telephone exchange service is terminated for purposes of interconnection to the public telephone network.

channel
A separate path through which voice or data can flow.

channel service unit (CSU)
The first device encountered by a T1 line entering a facility. The primary function of the channel service unit is to protect the equipment beyond it (from damage due to disturbances on the T1 line) and regenerate the signal to meet T1 specifications.

clear channel
A channel in which the entire 64Kbps bandwidth is available for customer information. In T1, this often requires a zero suppression technique, such as B8ZS.

client/server
A term describing the network architecture in which the computer processing is distributed among many individual PCs (clients) and a more powerful, central computer (server) that accepts requests for resources. Clients can share files and access data stored on the server.

coaxial cable
The standard in home cable television wiring. Coax is faster than twisted-copper pair, ISDN, or a T1.

codec
A coder/decoder device that converts video signals to/from digital for data transmission.

Competitive Access Provider (CAP)
An alternative carrier to local exchange carriers (LEC) for the provision of local loop to interexchange carrier (IXC) services.

Competitive Local Exchange Carrier (CLEC) See: Local Exchange Carrier (LEC)

Cross-Connect
An ATM switch usually comprising three functional areas. The three areas are system control, the central control unit, and the ATM "fabric block." Each of these functional system areas is configured according to the specified needs of the respective network node. Each functional area usually has its own monitoring and control units for safeguarding the high availability of the complete system.

Customer Premises Equipment (CPE)
Any equipment - such as telephones, computers, printers, video equipment, or other items - that a user can employ to connect to a network.

CSU See: channel service unit

Data Communications Equipment (DCE)
A device, such as a DSU (Data Service Unit) or modem, that provides an interface between a DTE (Data Terminal Equipment) device and a digital or dial network (also called data circuit-terminating equipment).

Data Service Unit (DSU)
A DCE device that interprets, interfaces, and provides timing and signal control between a DTE (Data Terminal Equipment) device and a digital network.

dedicated line
Leased or private communications line. Also called a dial-up line.

Demarcation Point (Demarc)
A demarc identifies the point where communications facilities owned by one organization interfere with that of another organization. This is the interface between customer premises equipment and network service provider.

digital
Digital uses bits and bytes to carry signals, as opposed to analog, which uses electronic waves together with sound waves. An analog signal is slower and easier to intercept and/or interfere with.

Digital Access and Cross-Connect System (DACS)
A piece of equipment usually operated by a TELCO and controlled by an external computer. It can cross-connect any T1 line attached to the DACS to any other T1 line, or any DS-0 channel or group of channels on a T1 line to any DS-0 time slots of any other T1 line.

Digital Data Service (DDS)
Examples: DATAPHONE, "Digital Service or ACCUNET," Spectrum of Digital. Services that provide digital, not analog, communication circuits.

distributed network
A computer network on which processing is shared by many different parts of the network. Processing may be shared by local computers, file servers, print servers, and application servers such as database servers. Distributed processing enables the most efficient use of processing power, because available processors can be assigned as either general or job specific processors. Distributed processing also enables duplication and distribution of key services, such as directory services, so that full services remain available regardless of the failure of individual parts of the network.

divestiture
The break-up of AT&T as a result of a settlement between the U.S. department of Justice and AT&T. Prior to 1984, AT&T was comprised of Bell Labs, AT&T Long Lines, Western Electric, and 22 Bell Operating Companies.

Direct Inward Dialing (DID)
Incoming PBX or Centrex (a service that permits incoming calls to be dialed direct) calls completed to extensions without the assistance of an operator.

Direct Access
Service available to Long Distance Carriers (IXCs), providing Business End-Users with a direct connection to the Local Exchange Carrier (LEC). Like Base Line Service, Direct Access is referred to as "bypass" service. Direct Access can be an economical alternative to the LEC.

distance learning network
A network of interconnecting schools, businesses, and institutions for the purpose of real-time, two-way interactive video. The Northwest Ohio Distance Learning Network provides area students with expanded curricula by offering classes via video.

domain name
Used for Internet purposes, this is a network associated with an organization, such as wired.com, or eff.org. Domain names are organized in a hierarchical system, with each level separated by a "dot." Organization types are commercial (.com), educational (.edu), organizational (.org), governmental (.gov), military (.mil), or network (.net). In the US, most Internet addresses follow a set format:
name__of__server.name__of__organization.type__of__organization.

downlink
The capture of the transmission of video and audio signals from a designated satellite by authorized users. A descrambling device is necessary for viewing encrypted signals.

DS-0 See also: voice grade lines
A circuit with the capacity or minimum bandwidth suitable for voice frequencies for "plain old telephony" (POTS) lines at 57Kpbs to 64Kbps.

DS-1 (Digital Signal 1)
A 24 DS-0 channel capacity circuit, with a transmission standard at T1 speeds, or 1.54 bits.

DS-3 (Digital Signal 3)
Transmission standard at T-3 speeds, or 44.736Mbps. DS-3 allows the combination of 28 DS-1s or a single DS-3 facility. A DS-3 is also known as a T3 circuit.

Electronic Data Interchange (EDI)
Series of standards that allow different companies and computers to exchange business documents over phone lines, computer-to-computer.

electronic mail (e-mail)
The electronic transmission and reception of messages and text-based information without the need for the recipient to be present at the time of the transmission. Available either as a value-added service from providers or on LAN systems.

encryption
Conversion of data into code for security purposes during transmission and decoding at the receiving end.

Ethernet
A high-bandwidth, local-area network primarily for personal computers; known by networking types as IEEE.802.3 (Institute of Electrical and Electronics Engineers) standard.

facilities-based
A company that has its own facilities available to its customers. The opposite of a reseller (a company that buys another company's services and resells and rebills its customers).

Federal Communications Commission (FCC)
U.S. agency which regulates communication by wire and radio, including the licensing of radio and television stations.

Fiber Distributed Data Interface (FDDI)
An optical-fiber-based, token-passing ring LAN technology with dual counter-rotating rings. Each ring carries data at a rate of 100Mbps using a 125MHz transmission frequency. It has been standardized by the American National Standards Institute (ANSI). An FDDI network has two modes of attachment: A device may be a Single Attach Station attached to one ring, or a Dual Attach Station attached to both rings. Typical applications of FDDI are in the area of high-speed LAN backbones.

fiber optics
(1) Means of providing a high-speed transmission, using light to send images through a flexible bundle of glass fibers. (2) Use of light as the primary medium in an actual application.

File Transfer Protocol (FTP)
An Internet protocol (IP) application for transferring files between network nodes.

firewall
Software that keeps unauthorized users or intruders from entering a network. Sometimes it also keeps company users on an internal network from browsing the Web.

Foreign Exchange
Circuit that connects a subscriber in one exchange with a Central Office in another exchange.

Fractional T1
A service in which a customer can use less than 24 channels on a T1 line without paying the cost of the entire line.

Frame Relay
A data communications interface originating from ISDN designed to provide high-speed frame or packet transmission with minimum delay and efficient use of bandwidth. It is a variation on the X.25 interface and a form of fast packet switching. Frame relay routes a packet directly to its destination, which increases throughput speeds. Like Ethernet and Token Ring, Frame Relay assumes that connections are reliable. Frame Relay does not have error detection or error control within the network, which also helps increase speed.

gateway
A "translator" machine or router that links two networks speaking different protocols. For example, e-mail sent from Explorer to the Internet passes through a mail gateway.

Gbps (Gigabyte)
One billion bytes.

head-end
A central point or hub in broadband networks that receives signals on one set frequency band and retransmits them or another. Every transmission in a broadband network has to go through the head-end. In CATV technology, the head-end is the control center for a cable system where video, audio, and data signals are processed and distributed along the coaxial cable network.

hub
The center of a star topology network or cabling system. A multi-node network topology that has a center multiplexer with many nodes feeding into and through the multiplexer or hub. The other nodes do not usually directly interconnect.

hypertext (http) A system of coding text that links electronic documents with each other. Elements in a hypertext document (i.e. words, pictures, etc.) are linked to elements in other documents. Click on a phrase and the screen reloads with a page of information about that idea; click on a picture and learn more about that visual.

InterExchange Carrier (IEC or IXC)
A company that provides interLATA (Local Exchange Carrier) telecommunications services, like AT&T, MCI, and U.S. Sprint. Access to these services can be provided through DDS dedicated channels, T1.5 dedicated access channels, or digital switched access (DSA) channels.

InterLATA
InterLATA calls are long-distance calls that originate in one LATA and terminate in another.

Incumbent Local Exchange Carrier (ILEC) See Also: RBOC
Term used to describe the established local phone company of a certain region before The Telecommunications Act of 1996.

Internet
The Internet has evolved into a worldwide network of computers communicating in a common language - TCP/IP - over telephone lines or microwave links. The Internet is home to the World Wide Web, where individuals, companies, and non-profit organizations may have a forum for their message.

Internet Protocol (IP)
The TCP/IP standard protocol that defines the IP datagram as the unit of information passed across the Internet and provides the basis for connectionless packet delivery service.

Intranet
In internetworking, applied to networks which utilize the technologies associated with the World Wide Web, but which are limited to a single company or organization. Used to distribute information within an enterprise using the flexible resources developed for the Internet, but without the security concerns associated with full Internet connectivity.

ISDN (Integrated Services Digital Network)
An approach to switched digital networking that can handle a range of digital voice, data, and digital image transmission. It is intended to provide end-to-end, simultaneous handling of digitized voice and data traffic on the same digital links via integrated switches. There are different access channels according to geographic location. These include Basic Rate Access and Primary Rate Access. ISDN standards are defined in the ITU-TS's (International Telecommunication Union-Telecommunication Standardization Sector) I-Series Recommendations.

IXC See: InterExchange Carrier

Kbps
Kilobits Per Second

LAN (Local Area Network)
A communications system that links computers into a network, usually via a wiring-based cabling scheme. LANs connect PCs, workstations, and servers together to allow users to communicate and share resources like hard disk storage and printers. A LAN is user owned and does not run over leased lines, although a LAN may have gateways to the PSTN or other private networks.

Long Distance Carrier See: InterExchange Carrier

LATA (Local Access and Transport Area)
A region served by a Local Exchange Carrier (LEC) that consists of one or more area codes.

Local Exchange Carrier (LEC)
Provider of local communication, i.e. Ameritech. Before The Telecommunications Act of 1996, a regional monopoly situation existed. Now, alternative companies may offer local voice, video, and data communication.

MAN See: Metropolitan Area Network

Mbps (Megabyte)
One million bytes.

media retrieval
Computer Control and Telephone Control that link the classroom to the media center across the network or telephone system. Utilizing 32-bit technology, all media center technology (VCRs, Laser Disk Players, etc.) is linked to a classroom computer.

Metropolitan Area Network
A high-speed network designed to link together sites in a metropolitan or campus area. The IEEE (Institute of Electrical and Electronics Engineers) has defined its 802.6 standard for MANs based on Distributed Dual Bus technology.

modem
Modulator/demodulator device that converts digital data to/from analog signals for transmission over analog facilities.

Multi-channel Multi-point (MCMP)
A circuit card that enables the support of up to six independent applications over a single mulitpoint digital facility. The MCMP capability can support up to 40 tributary DSUs, each optioned with an MCMP card.

Multiplexer
(1) Device that combines several slower speed circuits onto a higher speed circuit to improve transmission efficiency and provide value-added capabilities. (2) A device that can send several signals over a single line, separated by a similar device at the other end of the link. Examples of multiplexing include time division multiplexing, frequency division multiplexing, and statistical multiplexing.

network
A system that sends and receives data and messages, typically over a cable. A network enables a group of computers to communicate with each other, share peripherals (such as hard disks and printers), and access remote hosts or other networks.

network adapter
The hardware installed in workstations and servers that enables them to communicate on a network.

network anomaly
A problem on the network that causes an interruption in service. This interruption could result from a traffic accident downing fiber on poles, an animal or human digging up fiber, any type of cut, etc.

network interface board See: network adapter

network interface card See: network adapter

Network Interface Module (NIM)
The interface provided (up to two per carrier) for the public switched telephone network (PSTN) used by V.32 dial backup modules (DBMs) and dial/lease modems, and for the switched 56 kbps digital service used by the 2-wire and 4-wire Switched 56 DBMs.

Network Management System (NMS)
A set of diagnostic and configuration management tools for a data communication network, consisting of software programs and dedicated computer hardware; a distributed software controlled system for controlling and monitoring a network and diagnosing network problems.

Network Operations Center (NOC)
A centralized location and its staff responsible for the operational aspects of running a production network. The tasks include monitoring and control, troubleshooting, user assistance, etc.

network server See: server

node
Also referred to as a host, a device connected to a network, computer, printer, modem, or server to which data can be addressed.

NOS See: Network Operating System

Network Operating System (NOS)
The software that connects all the devices on a network so that resources can be shared efficiently and files can be transferred. The NOS handles the administration of network functions. A NOS is usually in two parts: server and client/requester.

OC-1 (Optical Carrier Level 1 Signal)
The lowest optical transmission rate in the SONET standard at 51.48Mbps.

OC-3 (Optical Carrier Level 3 Signal)
The second fastest optical transmission rate in the SONET standard at 155.52Mbps.

OC-N (Optical Carrier Level N Signal)
In SONET, a generic representation used to refer to the line rate being transmitted on a single mode fiber facility. A SONET transmission rate equal to N times the OC-1 line rate of 51.840Mbps.

Open Systems Interconnection (OSI)
A model for network communications consisting of seven layers that describe what happens when computers communicate with one another.

OSI See: Open Systems Interconnection

packet
The unit of information by which a network communicates. Each packet contains the identities of the sending and receiving stations, error-control information, a request for services, information on how to handle the request, and any necessary data that must be transferred.

per-call charge
Traditionally, the charge for a local phone call from the ILEC. (i.e. Ameritech in Toledo, Ohio).

Permanent Virtual Circuit (PVC)
A defined virtual link with fixed end points that are set up by the telecommunications carrier.

Plain Old Telephone Service (POTS)
A basic telephone voice line.

platform
Term used as a generic reference to all possible choices for some specific part of the computing environment. For example: desktop operating system platform (could include DOS, OS/2, and so on) or network operating system platform (NetWare, LAN Manager, and so on).

Point-to-point Circuit
A data network circuit with one control and one tributary.

point-of-presence (POP)
The physical location within a local access and transport area (LATA) where an interexchange carrier's circuits connect with the lines of the local telephone company serving that LATA.

port
Input/output connection for computer or communications equipment.

POTS See: Plain Old Telephone Service

PRI See: Primary Rate Interface

Primary Rate Interface (PRI)
ISDN's carrier or large user interface comprising 23B and 1D channels.

Private Branch Exchange (PBX)
A system that can transfer each line separately within an organization with only one direct line hook-up to a central office. An organization must have at least 50 lines for a PBX to be economical.

protocol
Set of rules that allows computers to connect to one another, specifying the format, timing, sequencing, and error checking for data transmission.

Public Switched Telephone Network (PSTN)
The nationwide telephone switching system operated by various telephone companies that enables the general public to communicate.

query
Process of extracting data from a database and presenting it for use.

real-time
Transmission (i.e. for a video conference) without any sound or visual delays.

redundancy
A duplicate capacity that can be called upon when a failure occurs; having more than one path to a signal point.

Regional Bell Operating Companies (RBOCs)
The regional Local Exchange Carriers established after the divestiture of 1983. Ameritech is the RBOC for Toledo, Ohio.

ring topology
A network layout that takes the form of a closed loop with the devices attached into the ring. A ring topology has self-healing capabilities, with communication rerouted around a network fault.

router
A software and hardware connection between two or more networks, usually of similar design, that permits traffic to be routed from one network to another on the basis of the intended destination of that traffic. A router located in a server is an internal router and external if located in a workstation.

server
A computer on the network capable of recognizing and responding to client requests for services. Services may range from basic file, printing, etc. to complex applications like database management.

Simple Network Management Protocol (SNMP)
A network management communications protocol originally developed by the Internet Engineering Task Force (IETF) for use on a TCP/IP network. Has been expanded for general use in managing distributed network devices and applications.

Simple Network Management Protocol Agent
Software or firmware in a network device supporting the SNMP protocol and functionality.

Simple Network Management Protocol Manager
A network management system designed to utilize the SNMP protocol and support devices that have SNMP Agents.

SONET See: Synchronous Optical NETwork

standalone
A computer that is not connected to a network.

star topology
A network layout or design in which each node is connected to a central hub. The hub establishes, maintains, and terminates all connections between the nodes.

switch
A switch is a network device that selects a path or a circuit for sending a unit of data to its destination. Private Branch Exchanges (PBX) are also commonly referred as a switch.

synchronous
Type of transmission in which the transmission and reception of all data is synchronized by a common clock and the data is usually transmitted in blocks rather than individual characters.

Synchronous Optical NETwork (SONET)
Transport network for synchronously multiplexed tributary signals. The standard defines a set of transmission rates, signals, and interfaces for fiber optic transmission. The broadband fiber network, which supports SONET, formed by a family of network elements conforming to the SONET interface requirements. The basic electrical signal runs at 51.840Mbps, approximately 51 times the bandwidth of a standard U.S., T1-leased line running at 1.544Mbps. SONET grows in multiples of the basic signal into the multi-gigabit range. SONET has the feature of adding and dropping lower bit-rate signals from the higher bit-rate signal without needing electrical demultiplexing.

Systems Network Architecture (SNA)
A description of the logical structure, formats, protocols, and operation sequences that transmit information and control the configuration and operation of a network.

T1
A U.S. and Japanese standard for high-speed data transmission at 1.544Mbps - 24 64Kibt/s channels. Also called a DS-1.

T-3
A U.S. and Japanese standard for high-speed data transmission at 44.736Mbps, providing the equivalent bandwidth of 28 T1 circuits. Also called a DS-3.

TCP/IP See: Transmission Control Protocol/Internet Protocol

Transmission Control Protocol/Internet Protocol (TCP/IP)
A protocol suite and related applications developed for the U.S. Department of Defense in the 1970s and 1980s specifically to permit different types of computers to communicate and exchange information with one another. TCP/IP is currently mandated as an official U.S. Department of Defense protocol and is also widely used in the UNIX (type of operating system) community.

Telecommunications Act of 1996
Passed by the Federal Government and implemented by the FCC, this law deregulates the local telephone industry. Now, for any given area of the country, other companies besides the RBOCs (Regional Bell Operating Companies) may offer local phone service. This is different from the 1983 deregulation that created competition in the long-distance phone industry. See divestiture.

telephony
The science of communication by telephone.

throughput
Net data transfer rate between an information source and an information destination.

toll
IntraLATA long distance or those calls within a LATA that are not considered to be local calls.

topology
The physical layout of network components (cable, stations, gateways, hubs, nodes, and so on). There are three basic interconnection topologies: star, ring, and bus networks.

twisted pair
(1) Insulated 18- to 26-gauge wire (e.g., telephone cables) in which pairs are twisted together to break the lines of flux that would induce electromotive force (EMF) signals in adjacent pairs because of the flow of electrical current. (2) Two wires, usually loosely spun around each other to help cancel out any induced noise in balanced circuits.

two-way interactive video
Capable of inbound and outbound visual and aural communication. The Northwestern Ohio Distance Learning Network is real-time, two-way interactive video at all hub sites.

uninterruptible power supply (UPS)
A backup power unit that provides continuous power even when the normal power supply is interrupted.

uplink
The transmission of video and audio signals to a designated satellite for distribution to authorized downlink sites. Transmission signals may be encrypted or unencrypted.

vector graphics (images)
Graphics displayed using a technology that specifies how an image is represented by using vector notation; for example, a starting point, a length, and the direction that the line to be drawn from the starting point is to take. From a mathematical perspective, a vector graphics image is simply a collection of individual lines or vectors.

video conferencing
Video and audio communication between two or more parties via a video-codec (coder/decoder) at either end, linked by digital circuits. Formerly needing in excess of 300Mbps bandwidth, systems are now available offering acceptable quality for general use at 128Kbps and high-quality 71KHz audio.

video-on-demand
A system of delivering programming without regard to schedules. The system implies that the viewer can press a button or dial a number and receive programming whenever he/she wishes. This can refer to pay-per-view events.

virtual
Conceptual or appearing to be, rather than actually being.

Virtual Private Network (VPN)
A virtual private network (VPN) is a way to use a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. A virtual private network can be contrasted with an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same capabilities, but at a much lower cost.

A VPN works by using the shared public infrastructure while maintaining privacy through security procedures and tunneling protocols, such as the Layer Two Tunneling Protocol (L2TP). In effect, the protocols, by encrypting data at the sending end and decrypting it at the receiving end, send the data through a "tunnel" that cannot be "entered" by data that is not properly encrypted. An additional level of security involves encrypting not only the data but also the originating and receiving network addresses.

voice grade lines (voice grade channel)
A channel or line offering minimum bandwidth suitable for voice frequencies, usually 300bits to 3.4Kbps. (See DS-0)

Voice Over Internet Protocol
VoIP (voice over IP: that is, voice delivered using the Internet Protocol) is a term used in IP telephony for a set of facilities that manage the delivery of voice information using the Internet Protocol (IP). In general, this means sending voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public switched telephone network (PSTN).

WAN (Wide Area Network)
Two or more LANs in separate geographic locations connected by remote telecommunications links.

wiring frame
Frame used to organize and manage the termination and connection of multiple cables.

workgroup
Two or more individuals on a LAN who share files, databases, and other resources.