专业英语的复习材料

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1、第八单元选择题1.TheearliestmethodofdeliveringtelecommunicationsistheTelegraph2.WithDigitaltechnology,theelectricalimpulsesonlyneedtocorrespondtotwodigitsinsteadofthefullrangeofqualitiesthatcomposetheoriginalmessage.3.A(n)Modemisadevicethatconvertsbetweenanaloganddigitalsignals,ma

2、kingitpossibleforacomputertotransmitinformationoverastandardtelephoneline.4.Datacommunicationsistheprocessoftransmittingandreceivingdatainanorderlywaysothedatathatarrivesatitsdestinationisanaccurateduplicationofthedatathatwassent.5.Basicdatacommunicationsconceptsarethebuil

3、dingblocksforunderstandinghowdatatravelsonacommunicationssystem.第九单元选择题1.Thesehigh-speeddataservicesareusuallyreferredtoasbroadbandconnections.ItisanticipatedthattheywillprovidethenecessarylinksbetweenLANsthatmakewhatiscalledtheinformationsuperhighwayareality2.Apublickeysy

4、stemallowsuserstoscrambleandunscrambletheirmessageseasilywithoutathirdpartyintruding.3.ThedevicesonaLANareknownasnodes,andthenodesareconnectedbycablingthroughwhichmessagesaretransmitted.NodesonaLANcanbewiredtogetherinanyofthreebasictopologies,knownasbus,ring,andstar.阅读理解Al

5、ocalareanetwork(LAN)isagroupofcomputersandotherdevicesdispersed(分散)overarelativelylimitedareaandconnectedbyacommunicationslinkthatenablesanydevicetointeractwithanyotheronthenetwork.LANscommonlyincludemicrocomputersandshared(oftenexpensive)resourcessuchaslaserprintersandlar

6、geharddisks.Most(modern)LANscansupportawidevarietyofcomputersandotherdevices.Eachdevicemustusetheproperphysicalanddata-linkprotocolsfortheparticularLAN,andalldevicesthatwanttocommunicatewitheachotherontheLANmustusethesameupper-levelcommunicationsprotocol.AlthoughsingleLANs

7、aregeographicallylimited(toadepartmentoranofficebuilding,forexample),separateLANscanbeconnectedtoformlargernetworks.SimilarLANsarelinkedbybridges,whichactastransferpointsbetweennetworks;dissimilarLANsarelinkedbygateways,whichbothtransferdataandconvertitaccordingtotheprotoc

8、olsusedbythereceivingnetwork.ThedevicesonaLANareknownasnodes,andthenodesareconnectedbycab