lesson90课件
日期：2010-03-19 03:42
telephoneszenghuiListentothetape&Answerthefollowingquestions1Howwasonetelephoneconnectedwithanotherinthepast?2Howisonetelephoneconnectedwithanothertoday?BythickheavymetalwiresByverythinglasspipesandsatellite2Readthetextloudlyandthenfindoutthemainideaofeachpara Para1________________Para2_______________Para3________________Para4_________________HowatelephoneworksTheearliesttelephonesThefirsttelephonedirectoryGreatadvancesinphoneequipmentOldtelephonesModerntelephonesWhydidpeoplehavetowindthehandlebeforemakingacall?Whatdidthetelephoneoperatordo?Whataresatellitesusedfor?AmericaChinaelectricalsignalselectricalsignalsHowdoesatelephonework?Lightsignalsvoice→voiceHear→electricalsignalselectricalsignalsWhatwasthewaytosendsignalsinthepast?metalwireslightsignalslightsignalsHowtosendsignalsnow?thinglasspipestoonoisy!notclear!veryclearelectricalsignalselectricalsignalsFindouttheusagesofthephoneintheoffice1234Conference，
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