Presentation on theme: "Lesson 90 Telephones What are they doing? Fast reading: How was one telephone connected with another in the past. How is one telephone connected with."— Presentation transcript:
Lesson 90 Telephones
What are they doing?
Fast reading: How was one telephone connected with another in the past. How is one telephone connected with another today? By thick heavy wires. By satellite; by very thin glass pipes.
Listen and answer 1. The number of telephone in 1990 is nearly ______ times as large as that in A B C. 100 D D
2. Which of the following is NOT true? ____ A. The first telephone was invented in B. Light signals are better than electrical signals. C. The thin glass pipes are cheaper than metal wires. D. The light signals almost don t get weaker over so long a distance. A
3. In the early days, you had to wind a handle____. A. to connect the number you wanted to call B. to produce enough power to make a call C. to tell the operator to make a call D. to change the waves of your voice into electrical signals B
4. People prefer to use light signal because _____. A. they are lighter B. they are cheaper to send C. they are simpler D. they are clearer D
5. How is a message changed on the telephone nowadays?_______. A.Sound waves electrical signals sound. B.Voice electrical signals light signals electrical signal sound. C. Sound waves light signals voice. D. Sound waveslight signalssound. B
watch paragraph 1 and answer
How does a telephone work? voice(sound wave)electrical signals a pair of lines the receiving phone electrical signals down to
Watch paragraph 2 and answer
1. Why were telephones not popular at the beginning? 2. Why were telephones expensive at the beginning? 3. Why did you have to wind the handle before making a call? 4. What did the telephone operator do? It was difficult to hear people over long distances. The wires which carried the telephone conversations were thick, heavy and expensive. To produce electricity. She connected the two numbers and made a note of the length of the telephone call and the charge.
The prototype of the first telephone invented by Alexander Graham Bell in It is made up of a coil of wire, a magnetic arm and a taut membrane(. Any sound causes the membrane, and hence the magnetic arm, to vibrate.
Early models of the telephone include Edisons 1879 wall- mounted phone (left), the candlestick design common in the 1920s and 1930s (bottom), and a 1937 cradle( telephone, a style popular since 1890 (right).
telephone USA 1878 directory 1877, , 300 million 1. When was the first telephone directory printed? And how many telephones in 1877 and in 1990? Read Paragraphs 3-4 and answer
Number of telephones in the world and in China ( ) (unit: million) In the worldIn China Fixed telephone Mobile phone
2. Why are light signals better than electrical signals? Electrical signalsLight signals Need to be strengthened every 3-4km Can travel 150km without getting weaker, signal is clearer Use very thin glass pipes instead of metal wires Get weaker and weaker as they travel Fibre optics (
watch paragraph 5 and answer
Can you describe the part that light signals played? Voice (sound)electrical signals light signals
electrical signals The way to send signals in the past metal wires light signals Nowadays thin glass pipes too noisy! not clear! very clear electrical signals electrical signals
some modern telephones
the ways in which new models of telephone can be used 1. conference calling 2. dialling 3. redirection 4. call waiting The telephone in the office
A B B c redirection
What would you do in the following situations? A.A friend of yours is ill and you hope shell soon be recovered B. You want to wish a friend good luck for an important exam. C. You want to find out if a friend is free to come to the cinema. Discussion Discuss these questions in pairs
Homework 1.Retell the text. 2.Finish off Wb exercises.