lesson 90 telephones what are they doing? fast reading: how was one telephone connected with another...
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 1877.
A. 1 000
B. 10 000
C. 100
D. 100 000
D
2. Which of the following is NOT true? ____
A. The first telephone was invented in 1873.
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 waves→light signals→sound.
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 （原型） of the first telephone invented by Alexander Graham Bell in 1875. It is made up of a coil （卷） of wire, a magnetic （磁的） arm and a taut （拉紧的） membrane( 薄膜） . Any sound causes the membrane, and hence the magnetic arm, to vibrate （振动） .
Early models of the telephone includeEdison’s 1879 wall-mounted （壁挂式） phone (left), the candlestick （烛台式） design common in the 1920s and 1930s(bottom), and a 1937 “cradle”( 支架式） telephone, a style popular since 1890 (right).
telephone ┌ USA 1878①
directory ├ 1877 ,2600②
└ ③1900 , 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 (2003.3 )
(unit: million)
In the world In China
Fixed telephone 1130 226
Mobile phone 1050 221
2. Why are light signals better than electrical signals?
Electrical signals Light 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 ( 光导纤维通讯）
watch paragraph 5 and answer
Can you describe the part that light signals played?
Voice (sound) electrical signals
electrical signals light signals
electrical signals
electrical signals
The way to send signals in the past
metal wires
light signals
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
conference calling
A
B
B
c
redirection
call waiting
What would you do in the following situations?A. A friend of yours is ill and you hope she’ll soon be recoveredB. You want to wish a friend good luck for an important exam.C. You want to find out if a friend is free to cometo the cinema.
Discussion Discuss these questions in pairs
Homework1. Retell the text.2. Finish off Wb exercises.