Make up sentences using the expressions above and the active words from the text.

UNIT V

TELEPHONY AND THE TELEPHONE

I. Reading comprehensive.

1. Learn your active vocabulary:

Sound wave:a vibration in the air, in water, etc. that we hear as sound.

Diaphragm:thin plate which moves easily when a small amount of pressure is applied to it.

To induce: toproduce an electric or magnetic effect at a distance.

Circuit:closed path around which a current can flow.

Switchboard:telephone switching center where a person controls the switching of lines.

Microphone:adevice for converting sound waves into electrical signals.

Insulator:material which does not allow current to flow.

Frequency:how often a pattern is repeated every second.

Coil:spiral of wire used as an inductor.

Fuse:electrical component used as a safety device which heats up and melts, breaking the circuit when the current becomes too large.

Sheath:close-fitting protective covering.

To convert:change from one form into another.

Read the text.

The Telephone

The first telephone was invented in 1876. Speech transmission in those days was limited to a distance of a few miles and the construction of the first telephone was simple. A wire with a ground provided the connection. The main parts were a transmitter and a receiver. Sound waves struck the diaphragm and caused it to vibrate. The vibration of the diaphragm changed the magnetic field, inducing electric waves of varying voltage and current. These waves passed to the distant telephone where the changes produced in the magnetic field caused the diaphragm to reproduce the original sound.

Later development of the telephone changed its construction, it became more complex. Transmitters and receivers were separated. Auxiliary elements were used in its circuit to provide for better transmission of speech. The need to connect any two of a large number of telephone sets led to the development of a switchboard in 1878. The advantage of a central switching office with a switchboard was very great. In 1889 telephone sets were interconnected automatically. Further development improved the switching system and more telephone constructions were used. The number of telephones to be interconnected increased and large cities needed more switchboard offices. Therefore the interconnection problem was of great importance. Central offices grew in number.

The construction of a telephone. When speaking over the telephone, we speak into the microphone or transmitter. The transmission of sounds over a distance is the transmission of oscillations. The frequency of the transmitted oscillations must be constant. The microphone or transmitter consists of microphone housing, carbon chamber, carbon diaphragm, carbon granules, insulating spacer, and conductor. The current passes through the diaphragm, carbon chamber and carbon granules. The sound pressure on the diaphragm varies the pressure on the granules of carbon. These granules either make more contacts and decrease the resistance of the granules, or make fewer contacts and increase the resistance. Sound waves produce oscillations of the same frequency as those of the sounding body. At these both the transmitter resistance and the current in the circuit will change.

The varying current passes through the receiver connected to a network. The receiver consists of electromagnet coils, a steel magnet and a diaphragm. The diaphragm, magnets and coil are housed in a plastic cap. A variable current passing through the magnet’s coils changes the position of the diaphragm; it makes it vibrate. The frequency of these oscillations is the same as that of the transmitter. Therefore, the receiver produces the same sounds which are spoken into the microphone.

Lines serving telephone sets may have contacts with power lines or with lightning. Therefore telephone sets and their lines need protection, and protector units serve as protection devices. Usually a protector unit consists of carbon protector blocks connected between each wire of the line and the ground. Fuses are also used on the protector blocks; they protect protector blocks against power contact currents. A fuse is an important part of protector blocks. Without it power contact currents may overheat the protector or its ground conductor. Sometimes fuses are not used. A fuse is not used if the building is served by insulated wires that are connected to metal-sheathed cables on the line pole.

The fax. Pictures can be transmitted over telephone by sound signals. A new apparatus does this by „looking’’ at the picture and sending what it sees over the telephone to an apparatus at the receiving end, which then converts the sound signals back into the picture. At the transmitting end, the photograph, picture or document is put into the apparatus. At the receiving end the reproduction appears on paper. Usually a photograph takes six minutes to be received and reproduced. In the apparatus optical devices begin rotating and picking up reflected light which passes through a filter. This is how the apparatus works.

3. Answer the following questions:

1. By what means is speech transmitted over a distance?

2. By what means are electric waves carried over a distance?

3. By what means are two telephone sets connected?

4. What parts does a telephone set include?

5. What parts does a receiver include?

6. What parts are linked to a common circuit?

7. What is the transmission of oscillations?

8. How many parts does the transmitter consist of?

9. What parts does current pass through?

10. What is the frequency of oscillations produced by sound waves?

11. Why does the receiver reproduce the same sounds which are spoken into the microphone?

12. Why do telephone sets need protection?

13. What units serve as protection device?

14. How can pictures be transmitted by telephone?

4. Read the following examples and translate them. Make sentences of your own:

1. You can reserve seats over the telephone.

2. I need to make a telephone call.

3. He’s on the telephoneat the moment.

4. I was about to phonethe police.

5. You’re wanted on the phone. (smb. wants to speak to you).

6. She is speaking to smb. by telephonenow.

5. Write all possible words connected with the word „telephone” (adjectives, nouns, verbs)

Make up sentences using the expressions above and the active words from the text.

7. Put each verb in brackets in the correct tense and form:

Many changes ----------(to take place) in telephone design in recent years. Formerly, telephones ---------(to have) rotary dials. A pulse --------- (to signal) each dialed number. Now, push-buttons---------(to replace) dials. Each button--------(to trigger) a different audio-frequency tone. This---------(to know) as multi-frequency dialing. Also, the handset---------(to change). Old models-----------(to contain) carbon microphones, which----------(to be) inexpensive and robust but noisy. Today, moving-coil and electric devices----------(to replace) the old microphones. Advances in technology----------(to allow) additional features to be added to phones. Most now-----------(to contain) memories to store frequently-used numbers. Some telephone manufacturers-----------(to add) LCDs which-----------(to display) dialed numbers and-----------(to indicate) the duration of calls.

8. Telephone expressions:

Finding your correspondent:

Can I / I’d like to speak to Ann, please.

Can you put me through to Peter Smith? Hello, is that Mr. Carter?

Identifying yourself:

This is Paul Simon (speaking). Paul Simon here.

Identifying the caller:

Who’s calling / speaking, please?

Could you give me your name, please? Which company are you from?

Asking caller to wait:

Hold on, please / Hold the line, please.

I’m trying to connect you.

Could you call back later? Can Mr. Simon call you back?

Explaining absence:

I’m afraid / I’m sorry, but he is in a meeting / with a client / off sick / on holiday.

Leaving a message:

Could you take a message? Could / Can I leave a message?

Taking a message:

Can I take a message? Would you like to leave a message?

I’ll pass on the message.

I’ll give him / her the message.

Dealing with problem:

I think you’ve got the wrong number.

Could you speak up – it’s a bad line.

Could you speak more slowly, please?

II. Grammar tasks.

Date: 2016-04-22; view: 1644