unit23telephone课件
日期：2010-09-07 09:14
信达中学魏文萍制作Answerthefollowingquestions1Howwasonetelephoneconnectedwithanotherinthepast?2Howisonetelephoneconnectedwithanothertoday?BythickheavymetalwiresBysatellite;byverythinglasspipeselectricalsignalselectricalsignalsWhatwasthewaytosendsignalsinthepast?metalwireslightsignalslightsignalsHowtosendsignalsnow?thinglasspipestoonoisy!notclear!veryclearelectricalsignalselectricalsignalsWhydidpeoplehavetowindthehandlebeforemakingacall?ToproduceelectricityWhatdidthetelephoneoperatordo?SheconnectedthetwonumbersandmadeanoteoftheLengthofthetelephonecallandthechargeWhataresatellitesusedfor?AmericaChinaForsendingtelephoneSignalsoverlongdistancesHowdoesatelephonework?1work?SpeakerphonethereceivingphoneReadthetextcarefullyandanswerthefollowingquestions:Question1(Para1)Voice→electricalsignals→electricalsignalsapairofwires→→soundwave(soundwave)Qu，
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