通信及基础工程28

Unit1TextAHistoryofTelecommunicationHistoryofTelecommunicationThehistoryoftelecommunicationbeganwiththeuseofsmokesignalsanddrumsinAfrica,theAmericasandpartsofAsia.Inthe1790s,thefirstfixedsemaphoresystemsemergedinEurope;howeveritwasnotuntilthe1830sthatelectricaltelecommunicationsystemsstartedtoappear.Thisarticledetailsthehistoryoftelecommunicationandtheindividualswhohelpedmaketelecommunicationsystemswhattheyaretoday.Thehistoryoftelecommunicationisanimportantpartofthelargerhistoryofcommunication.TextTextWordsNotesDiscussionHome1.AncientsystemsandopticaltelegraphyEarlytelecommunicationsincludedsmokesignalsanddrums.Talkingdrums1wereusedbynativesinAfrica,NewGuineaandSouthAmerica,andsmokesignalsinNorthAmericaandChina.Contrarytowhatonemightthink,thesesystemswereoftenusedtodomorethanmerelyannouncethepresenceofamilitarycamp.TextTextWordsNotesDiscussionHomeDuringtheMiddleAges,chainsofbeaconswerecommonlyusedonhilltopsasameansofrelayingasignal.Beaconchainssufferedthedrawbackthattheycouldonlypassasinglebitofinformation,sothemeaningofthemessagesuchas"theenemyhasbeensighted"hadtobeagreeduponinadvance.OnenotableinstanceoftheirusewasduringtheSpanishArmada,whenabeaconchainrelayedasignalfromPlymouthtoLondonthatsignaledthearrivaloftheSpanishwarships.

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TextWordsNotesDiscussionHomeFrenchengineerClaudeChappebeganworkingonvisualtelegraphyin1790,usingpairsof"clocks"whosehandspointedatdifferentsymbols.Thesedidnotprovequiteviableatlongdistances,andChapperevisedhismodeltousetwosetsofjointedwoodenbeams.Operatorsmovedthebeamsusingcranksandwires.HebuilthisfirsttelegraphlinebetweenLilleandParis,followedbyalinefromStrasbourgtoParis.TextTextWordsNotesDiscussionHomeHowever,semaphoreasacommunicationsystemsufferedfromtheneedforskilledoperatorsandexpensivetowersoftenatintervalsofonlytentothirtykilometers(sixtonineteenmiles).Asaresult,thelastcommerciallinewasabandonedin1880.TextTextWordsNotesDiscussionHomeTextTextWordsNotesDiscussionHome2.ElectricaltelegraphExperimentsoncommunicationwithelectricity,initiallyunsuccessful,startedinabout1726.ScientistsincludingLaplace,Ampère,andGausswereinvolved.ThefirstworkingtelegraphwasbuiltbyFrancisRonaldsin1816andusedstaticelectricity.TextTextWordsNotesDiscussionHomeCharlesWheatstoneandWilliamFothergillCookepatentedafive-needle,six-wiresystem,whichenteredcommercialusein1838.Itusedthedeflectionofneedlestorepresentmessagesandstartedoperatingovertwenty-onekilometers(thirteenmiles)oftheGreatWesternRailwayon9April1839.BothWheatstoneandCookeviewedtheirdeviceas"animprovementtothe[existing]electromagnetictelegraph"notasanewdevice.TextTextWordsNotesDiscussionHomeOntheothersideoftheAtlanticOcean,SamuelMorsedevelopedaversionoftheelectricaltelegraphwhichhedemonstratedon2September1837.AlfredVailsawthisdemonstrationandjoinedMorsetodeveloptheregister—atelegraphterminalthatintegratedaloggingdeviceforrecordingmessagestopapertape.Thiswasdemonstratedsuccessfullyoverthreemiles(fivekilometers)on6January1838andeventuallyoverfortymiles(sixty-fourkilometers)betweenWashington,D.C.andBaltimoreon24May1844.Thepatentedinventionprovedlucrativeandby1851telegraphlinesintheUnitedStatesspannedover20,000miles(32,000kilometers).Morse’smostimportanttechnicalcontributiontothistelegraphwasthesimpleandhighlyefficientMorseCode,co-developedwithVail,whichwasanimportantadvanceoverWheatstone’smorecomplicatedandexpensivesystem,andrequiredjusttwowires.3ThecommunicationsefficiencyoftheMorseCodeprecededthatoftheHuffmancodeindigitalcommunicationsbyover100years,butMorseandVaildevelopedthecodepurelyempirically,withshortercodesformorefrequentletters.TextWordsNotesDiscussionHome3.TelephoneTheelectrictelephonewasinventedinthe1870s;itwasbasedonearlierworkwithharmonic(multi-signal)telegraphs.Thefirstcommercialtelephoneservicesweresetupin1878and1879onbothsidesoftheAtlanticinthecitiesofNewHavenandLondon.AlexanderGrahamBellheldthemasterpatentforthetelephonethatwasneededforsuchservicesinbothcountries.Allotherpatentsforelectrictelephonedevicesandfeaturesflowedfromthismasterpatent.(tobecontinued)TextTextWordsNotesDiscussionHome(Continued)Creditfortheinventionoftheelectrictelephonehasbeenfrequentlydisputed,andnewcontroversiesovertheissuehavearisenfromtime-to-time.Aswithothergreatinventionssuchasradio,television,thelightbulb,andthedigitalcomputer,therewereseveralinventorswhodidpioneeringexperimentalworkonvoicetransmissionoverawire,whothenimprovedoneachother’sideas.4However,thekeyinnovatorswereAlexanderGrahamBellandGardinerGreeneHubbard,whocreatedthefirsttelephonecompany,theBellTelephoneCompanyintheUnitedStates,whichlaterevolvedintoAmericanTelephone&Telegraph(AT&T),attimestheworld’slargestphonecompany.TextTextWordsNotesDiscussionHomeThefirstcommercialtelephoneservicesweresetupin1878and1879onbothsidesoftheAtlanticinthecitiesofNewHaven,Connecticut,andLondon,England.Thetechnologygrewquicklyfromthispoint,withinter-citylinesbeingbuiltandtelephoneexchangesineverymajorcityoftheUnitedStatesbythemid-1880s.TheFirsttranscontinentaltelephonecalloccurredonJanuary25,1915.Despitethis,transatlanticvoicecommunicationremainedimpossibleforcustomersuntilJanuary7,1927whenaconnectionwasestablishedusingradio.TextTextWordsNotesDiscussionHome4.RadioandtelevisionOverseveralyearsstartingin1894theItalianinventorGuglielmoMarconibuiltthefirstcomplete,commerciallysuccessfulwirelesstelegraphysystembasedonairborneelectromagneticwaves(radiotransmission).InDecember1901,MarconiestablishedwirelesscommunicationbetweenSt.John’s,NewfoundlandandPoldhu,Cornwall(England),earninghimaNobelPrizeinPhysics(whichhesharedwithKarlBraun).In1900ReginaldFessendenwasabletowirelesslytransmitahumanvoice.TextTextWordsNotesDiscussionHomeFormostofthetwentiethcenturytelevisionsusedthecathoderaytubeinventedbyKarlBraun.ThefirstversionofsuchatelevisiontoshowpromisewasproducedbyPhiloFarnsworth,whodemonstratedcrudesilhouetteimagestohisfamilyinIdahoonSeptember7,1927.Farnsworth’sdevicewouldcompetewiththeconcurrentworkofKalmanTihanyiandVladimirZworykin.Thoughtheexecutionofthedevicewasnotyetwhateveryonehopeditcouldbe,itearnedFarnsworthasmallproductioncompany.In1934,hegavethefirstpublicdemonstrationofthetelevisionatPhiladelphia’sFranklinInstituteandopenedhisownbroadcastingstation.TextTextWordsNotesDiscussionHomeAftermid-centurythespreadofcoaxialcableandmicrowaveradiorelayallowedtelevisionnetworkstospreadacrossevenlargecountries.TextTextWordsNotesDiscussionHomeTelevisionisnotsolelyatechnologylimitedtoitsbasicandpracticalapplication.Itfunctionsbothasanappliance,andalsoasameansforsocialstorytellingandmessagedissemination.Itisaculturaltoolthatprovidesacommunalexperienceofreceivinginformationandexperiencingfantasy.Itactsasa“windowtotheworld”bybridgingaudiencesfromalloverthroughprogrammingofstories,triumphs,andtragediesthatareoutsideofpersonalexperiences.TextTextWordsNotesDiscussionHome5.SatelliteThefirstU.S.satellitetorelaycommunicationswasProjectSCOREin1958,whichusedataperecordertostoreandforwardvoicemessages.ItwasusedtosendaChristmasgreetingtotheworldfromU.S.PresidentDwightD.Eisenhower.TextTextWordsNotesDiscussionHomeTelstarwasthefirstactive,directrelaycommercialcommunicationssatellite.BelongingtoAT&Taspartofamulti-nationalagreementbetweenAT&T,BellTelephoneLaboratories,NASA,theBritishGeneralPostOffice,andtheFrenchNationalPTT(PostOffice)todevelopsatellitecommunications,itwaslaunchedbyNASAfromCapeCanaveralonJuly10,1962,thefirstprivatelysponsoredspacelaunch.Relay1waslaunchedonDecember13,1962,andbecamethefirstsatellitetobroadcastacrossthePacificonNovember22,1963.TextTextWordsNotesDiscussionHomeThefirstandhistoricallymostimportantapplicationforcommunicationsatelliteswasinintercontinentallongdistancetelephony.ThefixedPublicSwitchedTelephoneNetworkrelaystelephonecallsfromlandlinetelephonestoanearthstation,wheretheyarethentransmittedareceivingsatellitedishviaageostationarysatelliteinEarthorbit.Improvementsinsubmarinecommunicationscables,throughtheuseoffiber-optics,causedsomedeclineintheuseofsatellitesforfixedtelephonyinthelate20thcentury,buttheystillexclusivelyserviceremoteislandssuchasAscensionIsland,SaintHelena,DiegoGarcia,andEasterIsland,wherenosubmarinecablesareinservice.TextTextWordsNotesDiscussionHome6.ComputernetworksandtheInternetOnSeptember11,1940,GeorgeStibitzwasabletotransmitproblemsusingTeletype1tohisComplexNumberCalculatorinNewYorkCityandreceivethecomputedresultsbackatDartmouthCollegeinNewHampshire.Thisconfigurationofacentralizedcomputerormainframewithremotedumbterminalsremainedpopularthroughoutthe1950s.However,itwasnotuntilthe1960sthatresearchersstartedtoinvestigatepacketswitching—atechnologythatwouldallowchunksofdatatobesenttodifferentcomputerswithoutfirstpassingthroughacentralizedmainframe.(tobecontinued)TextTextWordsNotesDiscussionHome(Continued)Afour-nodenetworkemergedonDecember5,1969betweentheUniversityofCalifornia,LosAngeles,theStanfordResearchInstitute,theUniversityofUtahandtheUniversityofCalifornia,SantaBarbara.ThisnetworkwouldbecomeARPANET,whichby1981wouldconsistof213nodes.InJune1973,thefirstnon-USnodewasaddedtothenetworkbelongingtoNorway’sNORSARproject.ThiswasshortlyfollowedbyanodeinLondon.TextTextWordsNotesDiscussionHomeARPANET’sdevelopmentcenteredontheRequestforComment(RFC)5

processandonApril7,1969,RFC1waspublished.ThisprocessisimportantbecauseARPANETwouldeventuallymergewithothernetworkstoformtheInternetandmanyoftheprotocolstheInternetreliesupontodaywerespecifiedthroughthisprocess.InSeptember1981,RFC791introducedtheInternetProtocolv4(IPv4)andRFC793introducedtheTransmissionControlProtocol(TCP)—thuscreatingtheTCP/IPprotocolthatmuchoftheInternetreliesupontoday.Amorerelaxedtransportprotocolthat,unlikeTCP,didnotguaranteetheorderlydeliveryofpacketscalledtheUserDatagramProtocol(UDP)wassubmittedon28August1980asRFC768.Ane-mailprotocol,SMTP,wasintroducedinAugust1982byRFC821andhttp://1.0aprotocolthatwouldmakethehyperlinkedInternetpossiblewasintroducedonMay1996byRFC1945.TextTextWordsNotesDiscussionHomeInternetaccessbecamewidespreadlateinthecentury,usingtheoldtelephoneandtelevisionnetworks.TextTextWordsNotesDiscussionHomesemaphoren.臂板信号系统，（铁道）臂板信号装置opticaladj.视觉的，视力的；光学的telegraphyn.电信技术，超感beaconn.灯塔，信号浮标，烽火relayn.传递；继电器vt.转播；分程传递crankn.[机]曲柄vt.转动曲柄移动；使弯曲WordsWordsTextWordsNotesDiscussionHomepatentn.专利

vt.获得…专利，给予…专利权lucrativeadj.获利多的，赚钱的，合算的spanvt.跨越时间或空间empiricallyadv.以经验为主地harmonicadj.&n.和声的，谐和的

[物]谐波，和声transmissionn.播送，传送；传动装置transcontinentaladj.横贯大陆的，大陆那边的electromagneticadj.[物]电磁的WordsTextWordsNotesDiscussionHomecathoden.[电]阴极，负极silhouetten.轮廓，剪影；（事物的）形状coaxialadj.同轴的，共轴的communaladj.群体的，公民的，公共的telephonyn.电话学，电话，电话制造geostationaryadj.与地球的相对位置不变的configurationn.布局，构造；配置protocoln.（数据传递的）协议WordsTextWordsNotesDiscussionHome[1]Talkingdrum（话鼓）：西非的一种像沙漏形状的鼓，可通过声音的调节来模仿人类语言的语调和韵律，从而传递不同信息的鼓。

TextWordsNotesDiscussionNotesHome[2]OnenotableinstanceoftheirusewasduringtheSpanishArmada,whenabeaconchainrelayedasignalfromPlymouthtoLondonthatsignaledthearrivaloftheSpanishwarships.SpanishArmada：无敌舰队约有150艘以上的大战舰，3000余门大炮、数以万计士兵的强大海上舰队，最盛时舰队有千余艘舰船。这支舰队横行于地中海和大西洋，骄傲地自称为“无敌舰队”。本句的意思是：关于使用信号灯的一个很典型的例子是在西班牙无敌舰队时期，当一连串的信号灯从普利茅斯传递到伦敦时则示意了西班牙战舰的到来。TextWordsNotesDiscussionHome[3]Morse’smostimportanttechnicalcontributiontothistelegraphwasthesimpleandhighlyefficientMorseCode,co-developedwithVail,whichwasanimportantadvanceoverWheatstone’smorecomplicatedandexpensivesystem,andrequiredjusttwowires.Morsecode摩尔斯电码是一种时通时断的信号代码，通过不同的排列顺序来表达不同的英文字母、数字和标点符号。它发明于1837年，发明者有争议，是美国人塞缪尔·莫尔斯或者艾尔菲德·维尔。摩尔斯电码是一种早期的数字化通信形式，但是它不同于现代只使用零和一两种状态的二进制代码，它的代码包括五种：点、划、点和划之间的停顿、每个字符间短的停顿（在点和划之间）、每个词之间中等的停顿以及句子之间长的停顿。TextWordsNotesDiscussionHome本句的意思是：摩斯对于电报最重要的贡献是与韦尔一同发明的简单并且高效的摩斯电码，仅需要两根电线即可实现，这是在惠斯通复杂且昂贵的系统之上一次巨大的进步。TextWordsNotesDiscussionHome[4]Aswithothergreatinventionssuchasradio,television,thelightbulb,andthedigitalcomputer,therewereseveralinventorswhodidpioneeringexperimentalworkonvoicetransmissionoverawire,whothenimprovedoneachother’sideas.Aswith：正如；与…一样；就…来说；句中两个who引导两个定语从句修饰先行词inventors。本句意思是：正如其它伟大的发明，例如收音机、电视、电灯、数码电脑，都有一些发明家进行电线传输声音的先驱试验，然后在彼此的想法上不断改进。TextWordsNotesDiscussionHome[5]RFC（RequestForComments）：是一系列以编号排定的文件。文件收集了有关互联网相关信息，以及UNIX和互联网社区的软件文件。目前RFC文件是由InternetSociety（ISOC）赞助发行。基本的互联网通信协议都有在RFC文件内详细说明。TextWordsNotesDiscussionHomeQuestionsfordiscussion1.What’sthemainideaofthistext?2.Whatdoyoulearnaboutthefirstcommercialtelephone?3.HowdidSamuelMorsecontributetothedevelopmentoftelegraph?TextWordsNotesDiscussionHomeAnswerstoquestionsfordiscussionTextWordsNotesDiscussionHome1.What’sthemainideaofthistext?Thispassagegivesadetailedandbriefaccountofthehistoryoftelec