Lesson 7 data communication

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2. High speed data exchange between computers and/or other electronic devices via cable orwireless. 3. A code developed by Samuel Morse used for transmitting messages in which letters of the alphabet and numbers are represented by various sequences of written dots and dashes, or short and long signals such as electric tones or voltages. Morse code was used extensively in telegraphy. In a format that has beenstandardizedfor international use, it is still sometimes used for long distance radio communication. 4. By 1851, more than fiftytelegraph companies were inoperation. In 1874, a Frenchman EmileBaudot invented a telegraphmultiplexer and developed acode suitable for machineencoding and decoding. 5. In1876 telephone was invented by Dr. Alexander Graham Bell. Founder of the Bell Telephone Company by the year of 1877. 6. (Universal Automatic Computer) The first commerciallysuccessful computer,introduced in 1951 byRemington Rand. Over 40systems were sold. Itsmemory was made ofmercury-filled acousticdelay lines that held 1,00012-digit numbers. It usedmagnetic tapes that stored1MB of data at a density of128 cpi. 7. A medium through which a message is transmitted to its intended audience, such as print media orbroadcast (electronic) media. 8. A type of cable that consists of twoindependently insulated wirestwisted around one another. The useof two wires twisted together helpsto reduce crosstalk andelectromagnetic induction. Whiletwisted-pair cable is used by oldertelephone networks and is the leastexpensive type of local-areanetwork (LAN) cable, mostnetworks contain some twisted-paircabling at some point along theUTP CAT. 5Enetwork. Other types of cables usedfor LANs include coaxialcables and fiber optic cables. 9. Coaxial cabling is the primarytype of cabling used by thecable television industry and isalso widely used for computernetworks, such as Ethernet.Although more expensive thanstandard telephone wire, it ismuch less susceptible tointerference and can carry muchmore data. COAXIAL CABLE 10. Fiber optics is a particularly popular technology for local-area networks. In addition, telephone companies are steadily replacing traditional telephone lines with fiber optic cables. In FIBER-OPTIC CABLE the future, almost all communications will employ fiber optics 11. Microwave communication isthe transmission of signalsvia radio using a series ofmicrowave towers.Microwave communication isknown as a form of "line ofsight" communication,because there must benothing obstructing thetransmission of databetween these towers forMICROWAVE DATAsignals to be properly sentTRANSMISSIONand received. 12. Satellite is a specialized wirelessreceiver/transmitter that islaunched by a rocket and placedin orbit around the earth. Thereare hundreds of satellitescurrently in operation. They areused for such diverse purposes asweather forecasting, televisionbroadcast, amateurradio communications, Internetcommunications, and the Global SATELLITESPositioning System, (GPS). 13. In telecommunications, data transfer is usuallymeasured in bits per second. For example, a typical low-speed connection to the Internet may be 33.6 kilobits per second (Kbps). On Ethernet local area networks, data transfer can be as fast as 10 megabits per second. Network switches areplanned that will transfer data in the terabit range. 14. Bandwidth describes the maximum data transfer rateof a network or Internet connection. It measures howmuch data can be sent over a specific connection in a given amount of time. 15. Baseband refers to the original frequency range of atransmission signal before it is converted, or modulated, to a different frequency range. 16. refers to high-speed data transmission in which a single cablecan carry a large amount of data at once. The most common types of Internet broadband connections are cable modems(which use the same connection as cable TV) and DSL modems (which use your existing phone line). Because of its multiple channel capacity, broadband has started to replace baseband, the single-channel technology originally used in most computer networks. 17. The word modem is actuallyshort forModulator/Demodulator. Amodem is a communicationsdevice that can be either internalor external to your computer. Itallows one computer to connectanother computer and transferdata over telephone lines. Theoriginal dial-up modems arebecoming obsolete because oftheir slow speeds and are beingreplaced by the much faster cableINTERNET MODEMand DSL modems. 18. An external modem is a box thatattaches to a computers COMport via cables.EXTERNAL MODEM 19. A modem that resides onan expansion board that plugsinto a computer.INTERNAL MODEM 20. A device you can attach toa personal computer that enablesyou to transmit and receiveelectronic documents as faxes. Afax modem is like a regularmodem except that it is designedto transmit documents to a faxmachine or to another fax modem.Some, but not all, fax modems dodouble duty as regular modems. Aswith regular modems, fax modemscan be either internalor external. Internal fax modemsFAX MODEMare often called fax boards. 21. Multiplexer is a device that selects one ofseveral analog or digital input signals and forwards theselected input into a single line. 22. A type of multiplexor that combines multiple channels onto a single transmission medium in such a way that all the individual channels can be simultaneously active. 23. This processor is a computer that handles communicationsprocessing for a mainframe by connecting to thecommunications lines on one end and the mainframe on the other. It transmits and receives messages, assembles anddisassembles packets, and detects and corrects errors. Sometimes it is synonymous with a communications controller, although the latter is usually not as flexible.