新型消防车研究中英文翻译.docx
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新型消防车研究中英文翻译.docx
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新型消防车研究中英文翻译
附录4:
英文资料及中文翻译
1.英文资料
CommunicatingwithDatal
Datasignalsaretransmittedovervarioustypesoftelephonecircuits.Theytravelonwirefromtelephonepoletotelephonepole,throughundergroundcables,frommountaintoptomountaintopovermicrowavefacilities,ontheoceanfloorinsubmarinecables,andviacommunicationssatellitesfromcontinenttocontinent.Sometypeofdataconversionequipmentisrequiredtochangethedigitalmachinesignalstoaformsuitablefortransmissionoverthesefacilities.b5E2RGbCAP
Thedatamachinewhichprovidesaninputtothetransmitsectionoftheconversionequipment,ormodulator,canbeakeyboard,printer,cardreader,papertapeterminalcomputerormagnetictapeterminal.Theoutputfromthereceivesectionoftheconverter,ordemodulator,canbeappliedtoatapepunch,printer,cardpunch,magnetictapeunit,computer,orvisualdisplayterminal.Typically,boththemodulatoranddemodulatorsectionsoftheconverterarecombinedintoatwo-waydatatransmitter-receiver,commonlycalledadatamodemordataset.p1EanqFDPw
Thetypicalfull-duplexdatatransmissionsystemincludingtheoriginatingdataprocessingequipmentandtheinterfaceassemblywhichconsistsofbufferandcontrolunits.Theinterfaceassemblyatthetransmitteracceptsdataattheratedeterminedbytheoperatingspeedofthedataprocessor.storesthedatatemporarily,andregeneratesitataratecompatiblewiththatofthedatamodem.Atthereceivingterminaltheinterfaceassemblyacceptsthereceiveddata,storesit,thenfeedsittothedataprocessorattheappropriaterate.DXDiTa9E3d
Timingsignalsfromtheinterfaceassemblyatthetransmitterareappliedtothedatamodemtosynchronizethecomputerandthedataset.Atthereceiver,synchronizationpulsesarederivedfromthedatastreamtosynchronizethecomputer.RTCrpUDGiT
Whenmorethanonedatasetfeedsintoacomputer,thecapacityoftheinterfaceequipmentisofmajorconcernsinceitmustdeterminethetimeslotallocationforeachline.Varioustypesofinterfaceassembliesareemployed,suchasmagneticcorememories,shiftregisters,anddelaylines.Notalldatacommunicationsterminalsemployaninterfacebetweenthedataprocessorandthedatamodem.Withoutaninterface,theinput,datatransmission,andoutputfunctionsproceedsimultaneouslyandatthesamerateofspeed.5PCzVD7HxA
Sincedatasignalsarerarelyinsuitableformfortransmissionoverthevarioustypesoftransmissionfacilities,asignalcodingprocessisnormallyperformed.Ideally,thetransmissionmediumshouldhavelinearattenuationanddelaycharacteristics,butthisisneversoinpractice,andtransmissionimpairmentsarealwayspresenttodisturbthedatasignals.Asacomparison,invoicecommunicationsahighdegreeoftransmissionirregularitiescanbetolerated.Ifavoicecircuithasaheavylossorisnoisy,thespeakerscompensateautomaticallybyincreasingtheintensityoftheirvoices.Ifwordsaremissedbecauseoftransmissiondifficulties,theyareoftenunderstoodanywaybecauseoftheredundantnatureofspeech.Incontrast,thereisnoinherentredundancyindatasignalsunlesspurposelyinsertedand,therefore,transmissionvariationscaronlybecompensatedforoveraverysmallrange.Inaddition,datasignalsaresensitivetoothertransmissionimpairmentswhichhavelittleeffectonspeech.jLBHrnAILg
Codingisundertakentoalleviatetransmissionirregularities,toincreasetheinformationcapacityofthesystem,toenableerrordetection,andtoprovidemessagesecurity.Thecodingprocessinthedatatransmittersimplyrearrangestheapplieddatamachinesignalsintosomeotherformat.Atthereceivingendthereverseprocessingisperformedtorecovertheoriginalmachinesignals.xHAQX74J0X
Thediagramsshowthetwotypesofinformationsignalsthatareappliedindigitalformtoadatamodem.ShowninAisabinarynon-returntozerosignal.InBthesamesignalisshowninthereturntozeroformat.ThedifferencebetweenAandBisthatinAsuccessivemarksorspacesfollowoneanother,whereasinBtheremustbeareturntothespacelevelbetweensuccessivemarks.Thevoltagevaluesofmarksandspacesarearbitraryandmaybepositive,negative,orboth.LDAYtRyKfE
Ofprimaryconcernwhenconsideringthetransmissionofdatafromonedevicetoanotheriswiring.Andofprimaryconcernwhenconsideringthewiringisthedatastream.Dowesendonebitatatime,ordowegroupbitsintolargergroupsand.ifso,how?
Thetransmissionofbinarydataacrossalinkcanbeaccomplishedeitherinparallelmodeorserialmode.Inparallelmode,multiplebitsaresentwitheachclockpulse.Inserialmode,onebitissentwitheachclockpulse.Whilethereisonlyone-waytosendparalleldata,therearetwosubclassesofserialtransmission:
synchronousandasynchronous.Zzz6ZB2Ltk
Asynchronoustransmissionissonamedbecausethetimingofasignalisunimportant.Instead,informationisreceivedandtranslatedbyagreed-uponpatterns.Aslongasthosepatternsarefollowed,thereceivingdevicecanretrievetheinformationwithoutregardtotherhythminwhichitissent.Patternsarebasedongroupingthebitstreamintobytes.Eachgroup,usuallyeightbits,issentalongthelinkasaunit.Thesendingsystemhandleseachgroupindependently,relayingittothelinkwheneverready,withoutregardtoatimer.dvzfvkwMI1
Withoutasynchronizingpulse,thereceivercannotusetimingtopredictwhenthenextgroupwillarrive.Toalertthereceivertothearrivalofanewgroup,therefore,anextrabitisaddedtothebeginningofeachbyte.Thisbit,usuallya0,iscalledthestartbit.Toletthereceiverknowthatthebyteisfinished,oneormoreadditionalbitsareappendedtotheendofthebyte.Thesebits,usually1s,arecalledstopbits.Bythismethod,eachbyteisincreasedinsizetoatleast10bits,ofwhich8areinformationand2ormorearesignalstothereceiver.Inaddition,thetransmissionofeachbytemaythenbefollowedbyagapofvaryingduration.Thisgapcanberepresentedeitherbyanidlechannelorbyastreamofadditionalstopbits.rqyn14ZNXI
Thestartandstopbitsandthegapalertthereceivertothebeginningandendofeachbyteandallowittosynchronizewiththedatastream.Thismechanismiscalledasynchronousbecause,atthebytelevel,senderandreceiverdonothavetobesynchronized.Butwithineachbyte,thereceivermuststillbesynchronizedwiththeincomingbitstream.Thatis,somesynchronizationisrequired,butonlyforthedurationofasinglebyte.Thereceivingdeviceresynchronizesattheonsetofeachnewbyte.Whenthereceiverdetectsastartbit,itsetsatimerandbeginscountingbitsastheycomein.Afternbitsthereceiverlooksforastopbit.Assoonasitdetectsthestopbit,itignoresanyreceivedpulsesuntilitdetectsthenextstartbit.EmxvxOtOco
Theadditionofstopandstartbitsandtheinsertionofgapsintothebitstreammakeasynchronoustransmissionslowerthanformsoftransmissionthatcanoperatewithouttheadditionofcontrolinformation.Butitischeapandeffective,twoadvantagesthatmakeitanattractivechoiceforsituationslikelow-speedcommunication.Forexample,theconnectionofaterminaltoacomputerisana1uralapplicationforasynchronoustransmission.Ausertype’sonlyonecharacteratatime,typesextremelyslowlyindataprocessingterms,andleavesunpredictablegapsoftimebetweeneachcharacter.SixE2yXPq5
Insynchronoustransmission,thebitstreamiscombinedintolonger"frames",whichmaycontainmultiplebytes.Eachbyte,however,isintroducedontothetransmissionlinkwithoutagapbetweenitandthenextone.Itislefttothereceivertoseparatethebitstreamintobytesfordecodingpurposes.Inotherwords,dataaretransmittedasanunbrokenstringof1sand0s,andthereceiverseparatesthatstringintothebytes,orcharacters,itneedstoreconstructtheinformation.6ewMyirQFL
Itgivesaschematicillustrationofsynchronoustransmission.Wehavedrawninthedivisionsbetweenbytes.Inreality,thosedivisionsdonotexist。
thesenderputsasdataontothelineasonelongstring.Ifthesenderwishestosenddatainseparatebursts,thegapsbetweenburstsmustbefilledwithaspecialsequenceof0sand1sthatmeansidle.Thereceivercountsthebitsastheyarriveandgroupsthemineight-bitunits.kavU42VRUs
Withoutgapsandstart/stopbits,thereisnobuilt-inmechanismtohelpthereceivingdeviceadjustitsbitsynchronizationinmidstream.Timingbecomesveryimportant,therefore,becausetheaccuracyofthereceivedinformationiscompletelydependentontheabilityofthereceivingdevicetokeepanaccuratecountofthebitsastheycomein.y6v3ALoS89
Theadvantageofsynchronoustransmissionisspeed.Withnoextrabitsorgapstointroduceatthesendingendandremoveatthereceivingendand,byextension,withfewerbitstomoveacrossthelink,synchronoustransmissionisfasterthanasynchronoustransmission.Forthisreason,itismoreusefulforhigh-speedapplicationslikethetransmissionofdatafromonecomputertoanother.Bytesynchronizationisaccomplishedinthedatalinklayer.M2ub6vSTnP
ByfarthemostpopularserialinterfacebetweenacomputeranditsCRTterminalistheasynchronousserialinterface.Thisinterfaceissocalledbecausethetransmitteddataandthereceiveddataarenotsynchronizedoveranyextendedperiodandthereforenospecialmeansofsynchronizingtheclocksatthetransmitterandreceiverisnecessary.Infact,theasynchronousserialdatalinkisaveryoldformofdatatransmissionsystemandhasitsoriginintheeraofteleprompter.0YujCfmUCw
Serialdatatransmissionsystemsh
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