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1、装•ii四川信息职业技术学院0•2010—2011学年第一学期期末试卷（A）卷•订课程名称：《通信技术专业英语》课程代码：0231027考试方式：开卷考试时间:120分钟题号—b二三四五合计核分人题分2020102030100得分阅读下文，回答问题。Ourworldhasthreeseparateinformationinfrastructures:telephonesforvoice,televisionsforvideo,andcomputernetworksfordata.(1)Theseseparatevoice,video,anddatainf
2、rastructuresareallmovingfromanalogtodigitalfortransmission,multiplexing,andswitching.Thetelephoneinfrastructurehasbeendigitalinternallyforalongtile.Rightnow,thetelephonecompaniesaretryingtoorganizelowerenddigitalservicesthroughIntegratedServicesDigitalNetwork(ISDN).Thetelevisioni
3、nfrastmcturehasdeveloDedfromwirelesstocableandisnowusingfiberoplicmedia、butbroadcaststillremainsananalogtechnology・②Thenewestinformationinfrastructure,forcarryingdataamongcomputers,firstgrewwiththedevelopmentofpacket-switchingtechnologyinthe1970s・Packetswitchingwasusedtotransmitd
4、atatoconnectmainframesandminicomputersoverwideareanetworksaroundtheworld,®Multimegabitshared-mediaLANtechnologyinthe1980susedpacketswitchingtoconnectworkstationsandpersonalcomputerswithinbuildings.Ifyoifrethinkingitsabouttileforthetelephone,televisionandcomputernetworkinginfrastr
5、ucturestobeunifiedunderasingledigitaltechnology,youbegintounderstandATM,thegrandunifier.AsynchronousTninsferMode(ATM)isadigitalmultiplexingandswitchingtechnology.Itisdevelopedandstandardizedbytheworld'stelephonecompaniestointegratethetransmissionofvoice,video,anddatacommunication
6、s.Theproblemwithpacketswitchingforcomputernetworkingisthatifyouwanttomixinteractivevoiceandvideointoyourcomputernetworktransmissions,youarelimitedbywhatusedtobepacketswitchingsbasicstrength.本试卷由教务处监制Toefficientlytransfermillionsofbitspersecond,packetsaredifferentinlength,tendtobe
7、long,andareroutedonebyoneinsoftware.Thesequalitieshaveadvantages,especiallyoverthecircuitswitchingtechnologiestheyreplaced,buttheyresultindelaysthatleadtopoorvoiceandvideocommunications,especiallyatbillionsofbitspersecond・ATMovercomesthesedelayproblemsbyusingshortfixed-lengthpack
8、etscalledceils.End-to-endvirtualcircuitr
