| A | B |
|---|
| telecommunications | sending and receiving of information over telephone lines |
| bandwidth | number of bits that can be transferred per second over a given communications medium |
| analog signal | signal composed of continuous waves transmitted over a medium at a certain frequency range |
| bits per second (bps) | basic measurement of bandwidth |
| broadband medium | communications medium capabale of carrying a large amount of data at faster speeds |
| narrowband medium | communications medium capable of carrying samller amount of data at a slower speed |
| fiber-optic cable | consists of hundreds of tiny strands of glass or plastic material approximately the thickness of human hair; example of broadband medium |
| twisted-pair cable | originally developed for telephone networks; example of narrowband medium; one wire carries information; another wire is grounded and absorbs interference; used to connect computers in networks over short distances |
| digital signal | data in binary number system |
| communications medium | physical link that allows computers in different locations to be connected |
| modems | modulator/demodulator |
| dial-up modem | converts outgoing digital signal into analog form; converts incoming analog signal into digital signal |
| modulation | process of changing a digital signal into an analog signal |
| demoducation | refers to changing an analog signal into a digital signal |
| internal modem | electronic card inserted into an expansion slot on a computers motherboard; does not take up space on user's desktop |
| external modem | stand-alone device connected by cable to a computer's mother board; can be moved from one computer to another |
| infrared technology | technology that transmits data as light waves instead of radio waves |
| intranet | kind of network that only permits access to authorized users |
| network topology | term that refers to the pattern by which a network is organized |
| router | an electronic device thata ensures that messages are sent to their intended destination |
| hub | electronic device used in a LAN to link computers and allow them to communicate with one another |
| gateway | hardware and/or software that allows communication between two dissimilar networks |
| multiplexer | an electronic device that allows low-speed devices to simultaneously share a single high-speed communications medium |
| NetWare | popular LAN operating system developed by Novell Corporation |
| simplex transmission | directional protocol that allows data to flow in only one direction at a time |
| parallel transmission | group of 8 bits (plus a parity bit) are transmitted at the same time over 9 separate paths |
| serial transmission | bits are transmitted one bith after another in a continuous line |
| parity bit | extra bit added to ensure that there is always either a predetermined even number of bits or an odd number of bits |
| coaxial cable | commonly used for VCR and cable television connections, in telephone networks, and in some computer networks |
| baseband coaxial | often used in computer networks; about 3/8" thick; single channel for transmitting digital signals at about 10 mbps |
| broadband coaxial | used for cable television; has several channels each of which carry about 10 mpbs |
| mbps | Short for megabits per second, a measure of data transfer speed. Networks, for example, are generally measured in Mbps. |
| cable modem | allows cable subscribers to recive much faster data transmission speeds |
| splitter | used by a cable modem to connect on part to the television cable and the other part to the cable modem |
| ISDN | Integrated Services Digital Network; used to dial into the internet and transmit and receive information at very high speeds |
| T line | term coined by AT&T for a type of extemely high-speed telephone connection |
| T1 lines | allow for both voice and data communication; can carry data at 1.544 mbps; often leased by businesses to connect to the internet |
| T3 lines | faster than T1 lines; capable of carrying data at 44.7 mbpsused onlly by 50 largest U.S. corporations and major research labs; backbone of Internet |
| microwave system | transmit data through the atmosphere |
| communications satellite | solar-powered electronic device containing sever small, specialized radios called transponders |
| transponders | receive signals from transmission stations on teh ground |
| earth stations | transmission stations that send signals to transponders |
| geosynchronous orbit | orbits the earth at the same speed as the earth's rotation so the object appears stationary |
| POP server | Post Office Protocol; email messages are transferred to this server upon arrival at the receiving mail server; allows recipient to retrieve email |
| transmission of data over computer networks | characterized by bandwidth, as analog or digital, and as serial or parrallel |
| PCMCIA | type of modem used with notebook and other small computers |
| 57 million | number of T3 installations predicted to be installed by 2005 |
| node | device that is connected to and is part of a network |
| extranet | network that allows authorized employees, customers, and suppliers to access the company's internal computerized applications and data via the Internet |
| transceiver | electronic component of a network card that sends messages along a bus in either direction |
| star topology | multiple computes and peripheral devices are linked to a central computer (host) in a point-to-point configuration |
| bus topology | all computers (nodes) are linked by means of a single line of cable with two endpoints |
| ring topology | no host computer and each computer or workstation is connected to two other computers in a circular path |
| bridge | hardware and/or software that allows communications to occur between two similar networks |
| multiplexer | electronic device that transmits data from only one device at a time over a communications channel |
| client/server model | most common type of local area network (LAN) architecture |
| Hypertext Transfer Protocol (HTTP) | protocol that defines how Web pages are transmitted |
| Open Systems Interconnection (OSI) model | set of communication protocols defined by the International Organization for Standardization in Geneva, Switzerland |
| protocol | set of rules and procedures for exchanging information among computers in a network |
| synchronous transmission | blocks of bytes are wrapped in start and stop bytes called synch bytes |
| full-duplex transmission | transmission of information along a communications medium in both directions |
| half-duplex transmission | transmission of information along a communications medium in both directions, but in only one direction at a time |
| token ring protocol | protocol used by ring and star topologies that sends an electronic signal around the ring quickly |
| file transfer protocol (FTP) | used to transmit large files over the Internet |
| wireless application protocol (WAP) | protocol that enalbes wireless devices to access and use the Internet using a client/server network |
| simple mail transfer protocol (SMTP) | communications protocol used the transmit electronic mail |
| bps | basic measurement of bandwidth |
| local area networks (LANs) | make it convenient for multiple users to share programs, data information, hardware, software, and other computing resources |
| wireless keyboards | recent application of infrared technology |
| peer-to-peer network | network in which computers comprising the network have equivalent capabilities and responsibilities, each acting as both client and server |
| repeaters | specially desiged electronic devices that receive signals along a network, increase the strength of the signals, and then send the amplified signals along the network's communication path |
| asynchronous transmission | each byte of data is surrounded by control bits; transmitted at irregular intervals; usually involves a modem |
| synchronous transmission | blocks of bytes are wrapped in start and stop bytes called synch bytes; used by large computer systems; faster and more efficent way of sending data |
| hollow fiber | researchers believe this will be the next wave of fiber-optic cable |
| serial port | contained in modem that connects the sytem unit to a telephone line because the telephone line expects the data being transmitted to be in serial form |
| cellular technology | allows people to communicate wirelessly to and from nearly anywhere |
| metropolitan area network (MAN) | wide area network limited to a specific site, such as a city or town |
| file server | special computer used by LANs to house all the networks' resources |
| firewall | hardware and/or software that prevents or restricts access to and from a network |
| Wi-Fi protocol | protocol for wireless LAN technology; also called 802.11 protocol |
| America Online | a well-known value-added network |
| public access network (PAN) | wide area network operated and maintained by a large company which provides voice and data communications capabilities to customers for a fee |
| value added networks (VAN) | businesses that use the facilities of large communications companies to provide subscribers with additional services |
| virtual private network (VPN) | special type of Internet-based WAN |
