LESSON
5
TELEPHONE
I. Consider the
following
questions in
the group of
four. A
spokesperson will report
on your discussion
to the
whole group.
1. Do all the families in
2. What are telephones used for?
3. Who do you usually phone and why?
4. What number will you dial for fire brigade
or for ambulance in
5. What telephone would you like to have?
6. Why do you think telephones are still
popular with many people?
II.
Read the text below
and
answer the questions.
Telephone
Telephone is an instrument that
sends and receives voice messages and data. Telephones convert speech and data
to electrical energy, which is sent over great distances. All telephones are linked by complex switching systems called central
offices or exchanges, which establish the pathway for informa-tion to travel.
Parts
of a Telephone
A basic telephone set contains a transmitter that
transfers the caller's voice, a receiver that amplifies sound from an incoming call, a rotary or push-button dial, a ringerand a small assembly of
electrical parts, called the
antisidetone network, that keeps the caller's voice from sounding too loud
through the receiver. If
it is a two-piece telephone set, the
transmitter and rece-iver are mounted in the handset, the ringer is typically in the base, and the dial
may be in either the base or handset. The handset
cord connects the base to the handset, and
the line cord connects the telephone to the telephone
line.
More sophisticated telephones may
vary from this pattern. A speakerpho-ne has a microphone and speaker in the
base in addition to the transmitter and receiver in the handset. Speakerphones
allow callers' hands to be free, and allow more than two people to listen and
speak during a call. In a cord-less phone, the
handset cord is replaced by a radio link between the handset and base, but a
line cord is still used. This allows a caller to move about in a limited area
while on the telephone. A cellular phone has extremely miniatu-rized components that make it possible to
combine the base and handset into one handheld unit. No line or handset cords
are needed with a cellular phone. A cellular phone permits more mobility than a
cordless phone.
There are two common kinds of
telephone transmitters: the carbon transmitter and the electret transmitter.
The carbon transmitter is constructed by placing carbon granules between metal
plates called electrodes. One of the metal plates is a thin diaphragm that
takes variations in pressure caused by sound waves and transmits these
variations to the carbon granules. The electrodes conduct electricity that
flows through the carbon. Variations in pressure caused by sound waves hitting
the diaphragm cause the electrical resistance of the carbon to vary — when the
grains are squeezed together, they conduct electricity more easily; and when
they are far apart, they conduct electricity less efficiently. The resultant
current varies with the sound-wave pressure applied to the transmitter.
The electret transmitter is composed
of a thin disk of metal-coated plastic and a thicker, hollow metal disk. In the
handset, the plastic disk is held slightly above most of the metal disk. The
plastic disk is electrically charged, and an electric field is created in the
space where the disks do not touch. Sound waves from the caller's voice cause
the plastic disk to vibrate, which changes the distance between the disks, and
so changes the intensity of the electric field between them. The variations in
the electric field are translated into variations of electric current, which
travels across telephone lines. An amplifier using transistors is needed with
an electret transmitter to obtain sufficiently strong variations of electric
current.
The receiver of a telephone set is
made from a flat ring of magnetic material with a short cuff of the same
material attached to the ring's outer rim. Underneath the magnetic ring and
inside the magnetic cuff is a coil of wire through which electric current,
representing the sounds from the distant telephone, flows. A thin diaphragm of
magnetic material is suspended from the inside edges of the magnetic ring so it
is positioned between the magnet and the coil. The magnetic field created by
the magnet changes with the current in the coil and makes the diaphragm
vibrate. The vibrating diaphragm creates sound waves that replicate the sounds
that were trans-formed into electricity by the other
person's transmitter.
The alerter in a telephone is usually
called the ringer, because for most of the telephone's
history, a bell was used to indicate a call. The alerter responds
only to a special frequency of electricity that is sent by the exchange in res-ponse to the request for that telephone number.
The telephone dial has undergone
major changes in its history. Two forms of dialing still exist within the
telephone system: dial pulse from a rotary dial, and multifrequency tone, which
is commonly called by its original trade name of Touch-Tone, from a push-button
dial.
In a rotary dial, the numerals one
to nine, followed by zero, are placed in a circle behind round holes in a
movable plate. The user places a finger in the hole corresponding to the
desired digit and rotates the movable plate clockwise until the user's finger
hits the finger stop; then the user removes the finger. A spring mechanism
causes the plate to return to its starting position, and, while the plate is
turning, the mechanism opens an electrical switch the number of times equal to the
dial digit. Zero receives ten switch openings since it is the last digit on the
dial. The result is a number of "dial pulses" in the electrical
current flowing between the telephone set and the exchange. Equipment at the
exchange counts these pulses to determine the number being called.
The rotary dial has been used since
the 1920s. But mechanical dials are expensive to repair and the rotary-dialing
process itself is slow, especially if a long string of digits is dialed. The
development of inexpensive and reliable amplification provided by the
introduction of the transistor in the 1960s made practical the design of a
dialing system based on the transmission of relatively low power tones instead
of the higher-power dial pulses.
Today most telephones have push
buttons instead of a rotary dial. Touch-Tone is an optional service, and
telephone companies still maintain the ability to receive pulse dialing.
Push-button telephones usually have a switch on the base that the customer can
set to determine whether the telephone will send pulses or tones.
Comprehension Check Up
1. What
do we call an instrument for sending and
receiving voice messages and data? 2. What parts does
a basic telephone consist of? 3. Where are the transmitter and receiver placed? 4. What
are
the advantages of speakerphones compared with other kinds of phone? 5. Which
of the phones permits more mo-bility, a cellular phone
or a cordless one? 6. What substance is placed between
electrodes in the carbon transmitter? 7. What makes the electrical resistance of the carbon in the carbon transmitter vary? 8. What are the main parts of
the electrets transmitter? 9. Why does on electret transmitter contain an
amplifier using transistors? 10. What
does the receiver of a telephone contain? 11.
What dials are used nowadays? 12. What
are the disadvantages of the rotary dial? 13. Why does push – button telephones
have a switch on the base?
III.
Choose the best answer.
1. The best explanation of the expression to convert data might be…
a) to obtain facts; b) to arrange meeting at a
certain time; c) to change information from one form into another; d) to delete
information.
2. The word exchange
refers to …
a) a control office where telephone lines are
connected; b) a special-purpose telephone; c) money; d) movement from one place
to another.
3. The word transmitter
means…
a) a person who delivers messages;
b) an apparatus for sending out sig-nals, messages; c)
a part of a telephone that you hold
near to your ear; d) me-ans of convergence.
4. The word dial
implies …
a) a code of number for a telephone exchange;
b) a part of a telephone with numbers used to make a connection; c) apparatus
used to give a warning signal; d) a telephone conversation.
5. The word network means
…
a) material made by knotting a string; b) hard
work; c) defensive structures; d) a connected system.
6. The verb to mount means …
a) to separate; b) to create; c) to put and
fix; d) to make better.
7. The word sophisticated means…
a) large; b) complex; c) having a deep sound;
d) multi-channel.
8. The expression cordless phone refers to
…
a) the phone in which the handset is connected with the base by the
handset cord; b) the phone in which there are no lines or handset cords; c) the
phone in which there is a radio link between the handset and base; d) a
speakerphone
9. The verb to cause can be paraphrased as …
a) to change; b) to pay attention; c) to
suggest; d) to make happen.
10. The metal-coated plastic implies …
a) metal which is coated with plastic; b)
plastic which is covered with metal; c) plastic and metal covering; d) a layer
of plastic put on metal.
11. The best explanation of the flat
ring might be …
a) a wedding ring; b) a circular band worn
round a finger; c) a smooth and level band; d) a ring which is kept in a flat.
12. The verb to replicate means …
a) to repeat; b) b) remove; c) readdress; d)
rewrite.
13. The best explanation of the word clockwise might be…
a) the instrument for measuring and showing the
time; b) moving in the same direction as the hands of a clock; c) moving in the
direction opposite to that taken by the hands of a clock; d) the clock showing
the right time.
14. Optional
service means …
a) compulsory service; b) help or advice given
by manufacturers; c) the service which may be chosen or not as one wishes; d)
absent-subscriber service.
IV.
Use the
right verb from those given below.
to establish, to
provide, to replace, to rotate,
to vary, to link, to correspond, to determine, to contain, to
allow, to return, to maintain, to repair, to respond.
1. Telephone exchanges … all telephones and … the pathway for information to travel. 2. “Dial
pulses” are counted at the exchange … the number being called. 3. Transistor
… the development of inexpensive and reliable amplifica-tion.
V.
Are the following statements True or False?
1. In a two-piece telephone set, the transmitter
and receiver are placed in the handset; the ringer is usually in the base. 2.
The electrical transmitter consists of a thin disk, thick and hollow metal
base. 3. A device designed for amplification of sound from an incoming call is
called a receiver. 4. The telephone dial hasn’t changed since its invention. 5.
In a rotary dial zero follows the numerals one to nine.
VI.
Express the main idea
of each
paragraph
in one sentence.
VII.
Summarize the
text and be ready to retell it.
VIII.
Speak on the advantage.