Unit22telephones课件
日期：2010-05-13 05:47
Lesson90telephonesEarlytelephonesDesksettelephonesWalltelephonespresenttelephones1Tolearnthedevelopmentoftelephonesandinwhatwaystheyareusedintheoffice2TolearnhowatelephoneworksTeachingaims:(1847-----1922)wind…handletelephonedirectory(somethinginwhichyoucanlookuptelephonesnumbers)communicatepress…buttonshowatelephoneworksKeywordsorkeyphrasestheearliestphonesParagraph1Paragraph2Paragraph3Paragraphs4-5greatadvancesintelephoneequipmentthefirsttelephonedirectorypastnowadaysEffect:Wires:Waytomakeacall:Effect:Wires:Waytomakeacall:notveryclearthickheavyexpensivemetalwind…handle…electricity…operator…number…connectclearerverythinglasspipes…pressthebuttons_______________________________________________________________________________________________________________________________________________________________Lesson90telephonessoundwaveselectricalsignalssound___________________Howdoesatelephonework?soundwaveselectricalsignalslightsignalselectricalsignals(problem)_____________________________，
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