Unit 22 telephones课件（PPT 20页）.ppt

Teaching aims: 1. To learn the development of telephones and in what ways they are used in the office. 2. To learn how a telephone works. * Lesson 90 telephones Early telephones Desk set telephones Wall telephones present telephones ???????????????????????????????????????? (1847-----1922) wind …handle telephone directory (something in which you can look up telephones numbers) communicate press …buttons ???????????????????????????????????????? how a telephone works Key words or key phrases the earliest phones Paragraph 1 Paragraph 2 Paragraph 3 Paragraphs 4-5 great advances in telephone equipment the first telephone directory past nowadays Effect: Wires: Way to make a call: Effect: Wires: Way to make a call: not very clear thick.heavy expensive metal wind …handle…electricity…operator…number…connect clearer very thin glass pipes… press the buttons _____________________________________________________________ _____________________________________ _____________________________________________________________ Lesson 90 telephones sound waves electrical signals sound ____________ _______ *