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PAGEPAGE25Unit7computerbasic一：Technicalterms:1.arithmeticlogicunit（ALU）邏輯運算單元2.centralprocessingunit(CPU)中央處理器3.peripheraldevice外圍設(shè)備4.magnetictape 磁帶5.automaticassemblyline 自動裝配線6.I/Oports輸入/輸出端口7.agroupof一群8.beableto能，會9.inaddition另外10.respondto響應(yīng)，對應(yīng)于二：1.Translatethefollowingphrasesandexpressions.處理器processingunitAgroupoflogicallyrelatedinstructions一組邏輯相關(guān)的指令toreceiveinformationfromexternalequipment從外部設(shè)備接收信息中斷請求interruptrequesttobeabletofetchinstructionsfrommemory,decodetheirbinarycontents,executethem從存儲器中取出指令，并將二進制碼進行解碼,然后執(zhí)行三：TranslatethefollowingpassageintoChinese。RAMcontainsinformationbeingworkedonatthepresenttime.Itislikeanote-pad:theusercanreadtheinformationfromthismemoryandcanchangeitscontents.Whenthecomputerisswitchedoff,however,thismemoryiscompletelycleared.Asaresult,beforeyouturnoffyourcomputer,youshouldalwaysmakesuretosaveyourdataifyouwantitforanotherday.RAM包含目前正在處理的信息，它就像一本記事本，用戶可以閱讀儲存在上面的信息，可以改變它的內(nèi)容。然而，當計算機關(guān)機時，儲存在上面的信息完全刪除，因此，你關(guān)機前，你應(yīng)該確認你要儲存的有用數(shù)據(jù)。四：TranslatethefollowingsentencesintoEnglish存儲器可以用來存放指令和數(shù)據(jù)。Amemorycanbeusedtostoreinstructionsanddata.鍵盤是最常用的輸入設(shè)備。Keyboardisthemostcommonlyusedinputdevice.CPU可以響應(yīng)外部中斷請求信號。CPUcanrespondtotheinterruptsignalfromoutsideworld.

五：readingCentralprocessingunit（cpu）Informationfromaninputdeviceorfromthecomputer'smemoryiscommunicatedviathebustothecentralprocessingunit(CPU),whichisthepartofthecomputerthattranslatescommandsandrunsprograms.TheCPUisamicroprocessorchip??thatis,asinglepieceofsiliconcontainingmillionsoftiny,microscopicallywiredelectricalcomponents.InformationisstoredinaCPUmemorylocationcalledaregister.RegisterscanbethoughtofastheCPU'stinyscratchpad,temporarilystoringinstructionsordata.Whenaprogramisrunning,onespecialregistercalledtheprogramcounterkeepstrackofwhichprograminstructioncomesnextbymaintainingthememorylocationofthenextprograminstructiontobeexecuted.TheCPU'scontrolunitcoordinatesandtimestheCPU'sfunctions,anditusestheprogramcountertolocateandretrievethenextinstructionfrommemory.（1）howdoesinformationsendtoCPU?A．bycomponentsB．byregistersC．bybusD．bymemory（2）whichis(are)themainfunction(s)ofCPU?I.storesinformationII.TranslatescommandsIII.RunsprogramsA．IandIIIB．IandIIC．IIandIIID．bothofall（3）Howtokeeptrackofinstruction?A．useprogramcounterB．usebusC．usesiliconD．usetime（4）Programcounterisakindof____A．microprocessorB．registerC．softwareD．instruction（5）Inthecontext,whichpartofcomputerdoNOTmention?A．memorylocationB．controlunitC．inputdeviceD．outputdevice

Unit8internet一:Technicalterms:1.hostcomputer主機2.TheWorldWideWeb萬維網(wǎng)3.TCP/IP、傳輸控制協(xié)議/網(wǎng)際協(xié)議4.FTP文本傳輸協(xié)議5.DomainNames域名6.URLS統(tǒng)一資源定位7.DNS域名系統(tǒng)8.HTTP超文本傳輸協(xié)議9.HypertextDocuments.超文本文件10.SMTP簡單郵件傳輸協(xié)議11.POP郵局協(xié)議12.IMAP英特網(wǎng)消息訪問協(xié)議13.adial-uptelephonemodem調(diào)制解調(diào)器撥號上網(wǎng)14.andsoforth等等15.priorto在...之前16.viceversa反之亦然二：1.TranslatethefollowingphrasesandvidingaccesstooveronebillionWebpage提供對10億多網(wǎng)頁的訪問theagreeduponprotocolfortransmittingdatapacketsovertheWeb在網(wǎng)上傳輸數(shù)據(jù)包的公認協(xié)議在網(wǎng)上共享資源toshareresourceontheweb由服務(wù)提供商分配一個臨時地址toassignatemporaryaddressbyInternetServiceProvidertopermitsuserstotransferfilesfromtheservertotheirclientmachine允許用戶從服務(wù)器到客戶機傳遞文件三.TranslatethefollowingsentencesintoEnglish.1.典型的通信網(wǎng)包括：主機、網(wǎng)點、終端控制器和終端。AtypicalCommunicationNetworkincludes:hostcomputers,nodes,terminalcontrollers,terminals.2.英特網(wǎng)的優(yōu)勢在于它能夠方便快捷地傳遞信息。TheadvantageofInternetisthatitcantransmitinformationquicklyandeasily.3.網(wǎng)絡(luò)可看作是兩臺或多臺計算機的聯(lián)接。Anetworkcanbethoughtasacollectionoftwoormorecomputers.四、TranslatethefollowingpassageintoChinese.SMTP,POP,andIMAP:Sendinge-mailisoneoftheoldest,mostimportant,andfrequentlyusedInternetservices.SMTP(SimpleMailTransferProtocol)istheInternetprotocolusedtosendmailtoaserver.POP(PostOfficeProtocol)isusedbytheclienttoretrievemailfromanInternetserver.YoucanseehowyourbrowserhandlesSMTPandPOPbylookinginyourbrowser’sPreferencesorToolssection,wherethemailsettingsaredefined.YoucansetPOPtoretrievee-mailmessagesfromtheserverandthendeletethemessagesontheserver,orretainthemontheserver.IMAP(InternetMessageAccessProtocol)isamorecurrente-mailprotocolsupportedbymanyserversandallbrowsers.IMAPallowsuserstosearch,organize,andfiltertheirmailpriortodownloadingitfromtheserver.SMTP，POP，與IMAP：發(fā)送郵件是最老式、最重要也最常用的Internet服務(wù)項目。SMTP（簡單的郵件傳輸協(xié)議）是用于將郵件發(fā)送到服務(wù)器上的Internet協(xié)議。POP(郵局協(xié)議)被客戶用來從Internet服務(wù)器上取郵件的協(xié)議。通過查看瀏覽器的Preference或Toolssection（定義郵件設(shè)置的地方）就可以了解瀏覽器是是如何處理SMTP和POP的?？梢栽O(shè)置POP從服務(wù)器上取出E-MAIL信息，然后刪除或保留服務(wù)器上信息。IMAP（互聯(lián)網(wǎng)消息訪問協(xié)議）是一個較流行的郵件協(xié)議，它被許多服務(wù)器和所有瀏覽器支持。IMAP允許用戶在從服務(wù)器下載前搜索、組織和過濾郵件。五：reading（P47頁）1.Whatdowemainlyusecomputertodowhenwecommunicatewithpeople?A:toexchangeelectronicmessagesB:totransferfilesofinformationC:toaccessexpensivesharedresourcesD:alloftheabove2.Whatcomponentisnotincludedinatypicalnetwork?A:hostcomputersB:scannerC:terminalcontrollersD:terminals3.Thetwobasictypesofnetworksare_______.A:LANandWANB:LANandDNSC:WANandHTTPD:FTPandTCP4.Awide-areanetworkis2ormorecomputersthatlinkedbycommunicationfacilitiessuchas_______.A:telephonesystemB:microwaverelaysC:bothAandBD:noneoftheabove5.Whatarethebenefitsofnetwork?A:Itcantransmitinformationrapidlyandeasilyamongwidelyseparatedpeople.B:Peoplecansharehardwareandsoftwareresourcesonthenetwork.C:Acomputernetworkcanprovidehighreliabilitybyhavingalternativesourcesupply.D:Computernetworkcanhelpyoumakealotoffriendsandfindyourtruelove.Unit9AManualofSettingUpyourPC一：Technicalterms1.powercord 電源線2.initializationroutine 初始程序3.operatingsystem 操作系統(tǒng)4.warrantyregistrationcard保修卡5.setup建立…安裝6.ontopof在…之上7.switchon接通8.dependon依賴，取決于二：Translatethefollowingphrasesandexpressions.（1)toplacethePConadeskneartoeasilyaccessiblepoweroutlets將PC機放置在桌面上離電源插口較近的地方(2)打開PC包裝unpackyourPC(3)把鼠標、鍵盤、和顯示器連到計算機上connectmouse,keyboard,anddisplaytothecomputer（4)themodelnumberofyourdisplay你的顯示器的型號(5)tocompletetheWarrantyRegistrationcard填寫保修卡三;:FindandcorrectthemistakesmarkedA,B,C,Dinthefollowingsentences.Edisonhadtoinventfuses,whichwasanimportantsafetydevicebelovedDABC(A:fuse)AccordingtoitssizecomputersystemsareusuallydividedABCDintofourmaintypes.(B:their)Totheendof1880s,theelectricindustryhadbecomeaABCratherbigoneintheU.S.A.D(A:By)(4)Moderncommunicationprocessisinvolvedmanytechnologies.ABCD(B:involves)TheyareengagedindesigninganewtypeofcomputerratherABCthanrepairthemachine.D(D:reparing)四：TranslatethefollowingpassageintoChinese.Whatisacomputervirus(病毒)？Computervirusesaresmallprogramsthatreplicate(復制)byattachingacopyofthemselvestoanotherprogram.Acomputervirusisonekindofthreat(威脅)tothesecurity(安全性)andintegrityofcomputersystems.Likeotherthreats,acomputerviruscancausethelossoralterationofprogramsordata.Unlikemanyotherthreats,acomputerviruscanspreadfromprogramtoprogramandfromsystemtosystem,withoutdirecthumanintervention(介入).什么是計算機病毒？計算機病毒是小程序，該程序可以可以自我復制到另一程序上，計算機病毒對計算機系統(tǒng)的安全和完整性是一種威脅，計算機病毒可以引起程序或數(shù)據(jù)的丟失或改變。不同于其它的威脅，計算機病毒可以程序?qū)Τ绦蚧蛳到y(tǒng)對系統(tǒng)傳播，而沒有直接人為的介入。五：TranslatethefollowingChineseintoEnglish.請仔細閱讀一下這本計算機手冊。Pleasereadthiscomputermanualcarefully.將打印機的電纜連接到計算機的后面，旋緊螺絲。Connecttheprinter’scabletothebackofthecomputerandtightentheattachmentscrews.請將機內(nèi)的保單登記卡保存好。KeeptheWarrantyRegistrationCardinyourPCwell.TroubleShootingIfyourkeyboardormousedoesn’tworkEnsurethatthekeyboardormouseiscorrectlyconnected.Ensurethatthemousedriversuppliedwiththepreloadedsoftwareisinstalledcorrectly.Cleanthemouseballandtheroller.Ifyourprinterdoesn’tworkMakesuretheprinter’spowerswitchison.Verifythatthepowercordispluggedintothepoweroutletandtheprinter.Verifythatyouhavethecorrectcablefortheprinter.MakesurethatitissecurelyconnectedtothecorrectconnectoronthePCandtheprinter.Checkthattheprinterison-line.Examinethepaperfeedmechanismforapaperjam.MakesurethattheprinterisconfiguredcorrectlyforthePCandfortheapplication.EnsurethePC’sporthasbeencorrectlyconfiguredusingsetup.Makesuretheprinteriscorrectlysetupinwindow.Ensuretheapplicationprogram’s“print”menuhasbeencorrectlysetup.CheckthatthePC’sportisworkingproperlybyrunninganotherperipheralconnectedtotheport.Ifyoureceiveanerrormessage,refertotheprinter’smanualforhelp.1.Ifyourkeyboardormousedoesn’twork,whatshouldyoudotosolvetheproblem?A.Ensurethatthekeyboardormouseiscorrectlyconnected.B.Ensurethatthemousedriversuppliedwiththepreloadedsoftwareisinstalledcorrectly.C.Cleanthemouseballandtheroller.D.Alloftheabove.2.Whichofthefollowingisclosestinmeaningto“install”?A.setaboutB.setupC.takeawayD.takeoff3.Iftheprinterdoesn’twork,what’swrongwithit?A.Theprinter’spowerisoff.B.Thepowercordispluggedintothepoweroutletandtheprinter.C.Youhavethecorrectcablefortheprinter.D.Theprinterison-line.4.Yourprinterwillnotworkif______.A.Therepaperisnotjammed.B.thePC’sporthasbeencorrectlyconfiguredusingsetup.C.theprinteriscorrectlysetupinwindow.D.Theapplicationprogram“print”menuhasnotbeencorrectlysetup.5.Ifyoureceiveanerrormessage,whichoneofthefollowingyoushouldrefertofirstforhelp?A.Theprinter’sproducerB.Theprinter’ssellerC.Theprinter’smanualD.Theprinter’smaintenanceman

Unit12ISDN一：Technicalterms:1.Computer-aidedinstruction(CAI)計算機輔助教學2.homeappliance家用電器3.integratedservicedigitalnetwork(ISDN)綜合業(yè)務(wù)數(shù)據(jù)網(wǎng)CCITT(InternationalTelegraphandTelephoneConsultativeCommittee)國際電報電話咨詢委員會Takeadvantageof利用Dependupon取決于...define…as…把…定義為beresponsiblefor負責…二：.Translatethefollowingphrasesandexpressions.計算機輔助教學computeraidedinstruction(CAI)Homeappliance家用電器Tobecontrolledremotelybytheuserviathenetwork用戶通過網(wǎng)絡(luò)遠程控制(4)綜合業(yè)務(wù)數(shù)據(jù)網(wǎng)IntegratedServiceDigitalNetwork(ISDN)Takeadvantageofthiscommunicationtechnology利用通信技術(shù)三：TranslatethefollowingpassageintoChinese.Imagineanetworkthatwouldmakecommunicationsto,andbetween,entities(實體)ofaninsurance(保險)companyeasier.Whencallingacustomerserviceagent(機構(gòu)),thecustomer’srecordscouldautomatically(自動地)appearontheagent’sdisplay;thedisplayandthetelephonecallcouldbothbeforwardedtoanotheragent,ifnecessary.Claims(索賠)processingcouldbeexpedited(加快)byimprovingcommunicationsbetweentheagent,customer,andclaimsadjuster.Independentagentscouldaccessinsurancecompanydatabasestoquicklyexaminedifferentpolicyplansandcosts.可以想像網(wǎng)絡(luò)可以使保險公司與客戶之間的通信變得更容易。當呼叫客戶服務(wù)機構(gòu)時，客戶的記錄可以自動顯示在機構(gòu)的顯示頻上，而且顯示的資料和電話可以自動傳遞到另一家機構(gòu)。加強機構(gòu)、客戶、索賠解調(diào)員之間的通信聯(lián)系，索賠辦理就可以加快。獨立機構(gòu)可以進入保險公司的數(shù)據(jù)庫，很快地查詢到保險公司的不同政策計劃與收取費用。四.TranslatethefollowingsentencesintoEnglish.(1)網(wǎng)絡(luò)可以加強人們之間的溝通。Networkcanimprovethecommunicationbetweenpeople.(2)綜合業(yè)務(wù)數(shù)據(jù)網(wǎng)源于電話綜合數(shù)字網(wǎng)。ISDNoriginatesfromtelephoneIDN.(3)若采用ISDN，則語音和數(shù)據(jù)信息都可以在信道中傳輸。BothvoiceanddatainformationcanbetransmittedoverthechannelwithISDN.五：ReadingAnApplicationofISDNISDNcanstreamline(使簡化,使有效率;使現(xiàn)代化)theoperationofahospital,allowingmoreefficientdelivery(傳送)ofhealthcare.Thenetworkcouldprovidecommunicationsbetweenmajormedicalcenters,communityhospitals,anddoctor’soffice.Centraldatabasesandmedicalartificialintelligence(人工智能)systemscouldbemademoregenerallyavailable,eventohealthcarecenterswithlimitedfinancial(財務(wù)的)resources.Databasescouldmakethepostingandtrackingofpatientcareaswellasbillingeasierandmoreaccurate.Furthermore,thisinformationwouldbeavailabletothepatient’sprivatephysicianandtothis(oranother)hospitalincaseofasubsequent(一系列)readmission(重新接納)ortransfertoanotherfacility.Teleconferencingandelectronicmailcouldenhancestafftrainingandcommunications,makingnewmedicaltechnologiesandprotocolsmoregenerallyavailable.Inventorycontrolandaccesstoneedequipmentcouldbemoresimplyhandledusingacentralizedcomputer-basedsystem.Outpatient(門診病人)monitoringcouldbeonlyatelephonecallaway,regardlessofthepatient’slocation,allowingfasterresponsetopotentialemergencies(緊急情況),shorterhospitalstays,andfasterrecovery(恢復)times.1.Thenetworkcouldprovide______betweenmajormedicalcenters,communityhospitals,anddoctor’soffice.A.medicineB.communicationsC.doctorsD.nurses2.Whatisnottheadvantageofcentraldatabases?A.Centraldatabasescouldbemademoregenerallyavailable.B.Centraldatabasesaremoreexpensivetohealthcarecenterswithlimitedfinancialresources.C.Centraldatabaseswouldbeavailabletothepatient’sprivatephysician.D.Centraldatabaseswouldbeavailabletothehospitalincaseofasubsequentreadmissionortransfertoanotherfacility.3.Teleconferencingandelectronicmailcouldenhanceallofthefollowingexcept______.A.stafftrainingB.staffcommunicationsC.Makingnewmedicaltechnologiesandprotocolslessgenerallyavailable.D.Makingnewmedicaltechnologiesandprotocolsmoregenerallyavailable.4.Byusingacentralizedcomputer-basedsystem,Inventorycontrolandaccesstoneedequipmentcouldbe______.A.Moredifficulttohandle.B.morefrequenttohandleC.morecomplicatedlyhandledD.moresimplyhandled5.ISDNmakestheoutpatientmonitoringmoreefficientsuchas_____.A.fasterresponsetopotentialemergenciesB.shorterhospitalstaysC.fasterrecoverytimesD.alloftheabove

Unit13SignalsinCommunication一：Technicalterms1.signalprocessing信號處理2．discrete-timesignals離散時域信號3．continuous-timesignals連續(xù)時域信號4.digitalsignals數(shù)字信號5.analogsignals模擬信號6.betakenas被看作……7.specificto針對……8.convert……into……把……轉(zhuǎn)換成……9.bereferredtoas……被稱作……二：Translatethefollowingphrasesandexpressions.隨時間或空間變化的可測量的物理量anyquantitymeasurablethroughtimeoroverspaceasignalcodifiedmessage編碼的信號tobecarriedtoareceiverbythecommunicationschannel通過通信信道傳到接收機連續(xù)信號與離散信號continuousanddiscretesignalstwomaintypesofsignalsencounteredinpractice實際中主要會碰到兩種類型信號三：Fillintheblanksusingthesuitablechoice.(1)Eachversatilesignalgeneratorcanavirtuallyunlimitednumberofsignals.A.makeB.occurC.create(2)Trafficlights,whichmayalsobeknownastrafficsignals,stop-and-golights,robotsaresignalingdevicesatroadintersections.A.positionedB.putC.fixed(3)Themodulatedsignalonlyonesidebandandnocarrier.A.consistsofB.containsC.makesup(4)Thepowerrequiredisrelativelylargebecausethecarrier,whichcontainsnoinformation,isalongwiththeinformation.A.sentB.givenC.arranged(5)Incontrasttothetelephone,inradiocommunicationwhatismodulatedisacontinuouswaveradiosignal(carrierwave)producedbyaradiotransmitter.A.madeB.modulatedC.carried四.Fillintheblankswiththeproperpreposition.(1)therightsideofthefigure,thereistheequationgiventothattheorem.A.ByB.At C.To D.On(2)thiscase,itispossibletodeterminetheamplitudeofthevoltage.A.AtB.WithC.InD.On(3)Theamplifiercouldbeanytypeusingvalveortransistortechnologyateitheraudioorradiofrequencies.A.inB.at C.of D.as(4)Everypulseinthelaserbeamisinstepeveryotherpulse.A.with B.to C.uponD.at(5)highfrequenciestheloadsmaybeinductive.A.At B.On C.For D.From4.TranslatethefollowingpassageintoChinese.WithBogusBus,oursignalswereverysimpleandstraightforward:eachsignalwire(1through5)carriedasinglebitofdigitaldata,0Voltsrepresenting"off"and24VoltsDCrepresenting"on."Becauseallthebitsarrivedattheirdestinationsimultaneously,wewouldcallBogusBusaparallelnetworktechnology.IfweweretoimprovetheperformanceofBogusBusbyaddingbinaryencoding(tothetransmitterend)anddecoding(tothereceiverend),sothatmorestepsofresolutionwereavailablewithfewerwires,itwouldstillbeaparallelnetwork.If,however,weweretoaddaparallel-to-serialconverteratthetransmitterendandaserial-to-parallelconverteratthereceiverend,wewouldhavesomethingquitedifferent.采用BogusBus技術(shù)，信號簡單直觀。每位信號線（1-5）攜帶一位數(shù)字信息，0伏代表“關(guān)”，直流24伏代表“開”。由于所有位同時到達終端，我們稱BogusBus為并行網(wǎng)絡(luò)技術(shù)。假如我們通過加進二進制編碼（發(fā)送端）和解碼（接收端）改進BogusBus技術(shù)，這樣可以少用幾根導線，但這仍然是并行網(wǎng)絡(luò)。假如我們在發(fā)送端加入并行-串行轉(zhuǎn)換器，在接收端再加入串并轉(zhuǎn)換器，情況就不一樣了。五.TranslatethefollowingsentencesintoEnglish.圖像可以看成是一種信號.Imagecanbetakenasakindofsignal數(shù)字信號是離散信號。ReadingDigitalsignalisakindofdiscretesignal.電話可以將語音信號轉(zhuǎn)換成電信號。Telephonecanconvertvoicesignalintoelectricalsignal.六：Passage:PracticalSignalSoundSinceasoundisavibrationofamedium(suchasair),asoundsignalassociatesapressurevaluetoeveryvalueoftimeandthreespacecoordinates.Amicrophoneconvertssoundpressureatsomeplacetojustafunctionoftime,usingavoltagesignalasananalogofthesoundsignal.Compactdiscs(CDs)CDscontaindiscretesignalsrepresentingsound,recordedat44,100samplespersecond.Eachsamplecontainsdataforaleftandrightchannel,whichmaybeconsideredtobea2-vectorsignal(sinceCDsarerecordedinstereo).PicturesApictureassignsacolorvaluetoeachofasetofpoints.Sincethepointslieonaplane,thedomainis2-dimensional.Ifthepictureisaphysicalobject,suchasapainting,it’sacontinuoussignal.Ifthepictureisadigitalimage,it’sadiscretesignal.It’softenconvenienttorepresentcolorasthesumoftheintensitiesof3primarycolors,sothatthesignalisvector-valuewithdimension3.VideosAvideosignalisasequenceofimages.Apointinavideoisidentifiedbyitsposition(2-dimensional)andbythetimeatwhichitoccurs,soavideosignalhas3–dimensionaldomain.Analogvideohas1continuousdomaindimension(acrossascanline)and2discretedimensions(frameandline).1.Whichofthefollowingisnottrue?A.Sinceasoundisavibrationofamedium.B.Asoundsignalassociatesapressurevaluetoeveryvalueoftimeandthreespacecoordinates.C.Amicrophoneconvertsairpressuretoonlyafunctionoftime.D.Amicrophoneusesavoltagesignalasananalogofthesoundsignal.2.CDscontaindiscretesignalsrepresentingsound,recordedat________samplespersecond.A.44,010B.44,0013.Eachsamplecontainsdataforaleftandrightchannel,whichmaybeconsideredtobea____-vectorsignal.A.1B.24.Whatofthefollowingistrueaboutpictureaccordingtothetext?A.Apictureassignsacolorvaluetoeachofasetofpoints.Thedomainis3-dimensional.B.Ifthepictureisaphysicalobject,suchasapainting,it’sadiscretesignal.C.Ifthepictureisadigitalimage,it’sacontinuoussignal.D.It’softenconvenienttorepresentcolorasthesumoftheintensitiesof3primarycolors,sothatthesignalisvector-valuewithdimension3.5.Whatofthefollowingisnottrueaboutvideoaccordingtothetext?A.Avideosignalisasequenceofimages.B.Apointinavideois3-dimensional.C.Avideosignalhas3–dimensionaldomain.D.Analogvideohas1continuousdomaindimension(acrossascanline)and2discretedimensions(frameandline).

Unit14Pulse-CodeModulation一：Technicalterms1.Pulse-CodeModulation(PCM)脈沖編碼調(diào)制2.digitalpulse數(shù)字脈沖3.analog-to-digital(A/D)converter模/數(shù)轉(zhuǎn)換器4.rectangularpulse矩形脈沖5.cutofffrequency截止頻率6.low-passfilter低通濾波器7.asequenceof一系列的8.atrainof一連串的9.liein在于10.bymeansof借助于11.achainof一連串的12.beequalto等于，與…相等二：Translatethefollowingphrasesandexpressions.(1)thedigitalpulsemodulation數(shù)字脈沖調(diào)制(2)數(shù)/模轉(zhuǎn)換器digital-to-analogueconverter(3)thetrainofquantizedsamples一系列量化脈沖(4)thevariousoperationsthatconstituteabasicPCMsystem構(gòu)成基本PCM系統(tǒng)的不同操作(5)repeaterslocatedsufficientlyclosespacingalongthetransmissionroute.傳輸線上的中繼器間隔緊湊Translatethefollowingsentences,payingmoreattentiontothemeaningsof“with”.(1)Withthesenewmethodsofmakingelectroniccircuitswecanbesurethattheelectronicdeviceofthefuturewillbecomequitesmall.采用制作電子電路的新方法,我們可以確定:未來的電子裝置將變得更小。(2)Peopleonthenetdiscoveredthattheycouldexchange（交換）messagesandconductelectronic“conference”withdistantcolleges.網(wǎng)絡(luò)上的人們發(fā)現(xiàn)他們可以與遠方的同事交換信息，舉行電子會議。(3)Auserwithanaccount(賬戶)onanyInternetmachinecanestablishaliveconnectiontoanyothermachineonthenetfromtheterminalinhisownofficeorlaboratory.在因特網(wǎng)上開戶的用戶，可以從他們自己的辦公室或?qū)嶒炇医K端與任意其它網(wǎng)絡(luò)建立連接。(4)Withtheintroductionofdigitaldatasystem(DDS),somesubscribesthattransmitdigitalsignalshavebeenincorporated(并入)intothenetwork.由于數(shù)字化數(shù)據(jù)系統(tǒng)的出現(xiàn)，一些傳送數(shù)字信號的客戶已經(jīng)并入該網(wǎng)。(with,由于)(5)Theelectricfieldwouldchangewithtime.電場隨時間變化而變化。(6)BecauseATMisasynchronous(異步的),timeslotsareavailableondemandwithinformationidentifyingthesourceofthetransmissioncontainedintheheaderofeachATMcell.由于ATM是異步傳輸?shù)?，時隙可以根據(jù)包含在每個ATM信元頭中的傳輸信源的識別信息要求來獲得。四：TranslatethefollowingpassageintoChinese.Toensureperfectreconstructionofthemessagesignalatthereceiver,thesamplingratemustbegreaterthantwicethehighestfrequencycomponentWofthemessagesignalinaccordancewiththesamplingtheorem.Inpractice,alow-passanti-aliasingfilterisusedatthefrontendofthesamplertoexcludefrequenciesgreaterthanWbeforesampling.Thustheapplicationofsamplingpermitsthereductionofthecontinuouslyvaryingmessagesignaltoalimitednumberofdiscretevaluespersecond.為了確保接收機中信源不失真的解調(diào),根據(jù)取樣定理,取樣率應(yīng)大于信源最高頻率成分W的兩倍。實際應(yīng)用中，線性低通濾波器用于取樣器的前端，以消除取樣前高于W的頻率分量。因此，取樣應(yīng)用時允許連續(xù)變化的信源信號取樣成每秒有限個離散值。五：TranslatethefollowingsentencesintoEnglish.(1)所謂編碼就是把量化后的信號變換成代碼的過程。Theso-calledencodingisaprocessinwhichquantizedsignalisconvertedintoacode.(2)PCM是語音編碼的主要形式之一。PCMisoneofthebasicformsofvoiceencoding.(3)編碼不僅可用于通信，還廣泛應(yīng)用于計算機、數(shù)字儀表等領(lǐng)域。Encodingisnotonlyusedincommunication,butalsowidelyusedinthefieldsofcomputer,digitalinstruments.六：ReadingModulationanddemodulationcommunicationModulationincommunications,processinwhichsomecharacteristicofawave(thecarrierwave)ismadetovaryinaccordancewithaninformation-bearingsignalwave(themodulatingwave);demodulationistheprocessbywhichtheoriginalsignalisrecoveredfromthewaveproducedbymodulation.Theoriginal,unmodulatedwavemaybeofanykind,suchassoundor,mostoften,electromagneticradiation,includingopticalwaves.Thecarrierwavecanbeadirectcurrent,analternativecurrent,orapulsechain.Inmodulation,itisprocessedinsuchawaythatitsamplitude,frequency,orsomeotherpropertyvaries.Whentheamplitudeofhighfrequencycarrierwaveischangedinaccordancewiththeintensityofthesignal,itiscalledamplitudemodulation.Inamplitudemodulation,onlytheamplitudeofthecarrierwaveischangedinaccordancewiththeintensityofthesignal.However,thefrequencyofthemodulatedwaveremainsthesameasthecarrierfrequency.Notethattheamplitudeofbothpositiveandnegativehalfcycles(周期)ofcarrierwavearechangedinaccordancewiththesignal.Forinstance,whenthesignalisincreasinginthepositivesense,theamplitudeofcarrierwavealsoincreases.Duringnegativehalfcycleofthesignal,theamplitudeofthecarrierdecreases.Amplitudemodulationisdonebyanelectroniccircuitcalledmodulator.Inamplitudemodulation,theamplitudeofthewaveisvariedduplicatingfaithfullythefluctuationsofthemessage.Atthereceiverthesevariationsaredetectedormodulatedi.e.,themessageisremovedfromthecarrier.(Althoughthemoreprecisetermsaredemodulationfortheprocessanddemodulatorforthedevice,thetermsdetectionanddetectorarewidelyused.)Afterreceptionanddemodulationatthereceiver,thecarrierisofnofurtheruseandisdiscarded.Correspondingtodifferenttypesofmodulationprocesses,therearedifferenttypesofdemodulation.Fordemodulation,themodulatedwaveisfedtoacirc