TELECOMMUNICATIONS OPERATION PRINCIPLES

TELECOMMUNICATIONS OPERATION PRINCIPLES

AIM:

To recognize the English technical terms related to the operation of telecommunication systems and devices;

OBJECTIVES:

On successfully completing this unit the student should be able to:

identify correctly the terms describing signal creating-, receiving-, transmitting processes;

recognise the specific terms related to signal encoding and decoding procedures and the corresponding devices;

describe the separate stages in the operation of telegraph-, telephone-, radio-, television-, and internet communications and identify similarities and differences;

identify the types of equipment used for each type of signal creation, transmission and reception and compare them;

describe the function performed by each device;

assimilate at least 30 terms specific of signal creating-, receiving-, transmitting processes and equipment;

KEY TERMS:

convert, digital format, mathematical format, transmission, decode, modulated electrical impulses, via, modulation, contact, telegraph key, metal conductor, electrical impulse, burst of sound, dots and dashes, diaphragm, wire coil, analogue waveform, electrical waveform, speaker, cellular radio telephones, broadcast radio, electromagnetic radiation, microwave, wavelength, frequency, encode, amplitude, tuner, picture tube, electron gun, photo-sensitive display screen, analogue transmission, series of binary numbers, digits, network, broadband networks, cable television company, modem, modulator/demodulator, transmission media, copper wires, fibre-optic cable, communication satellite, microwave radio, wire-based (or wire line) telecommunications, wireless communications, cordless telephone, pager, satellite, high-speed Internet access.

How Telecommunications Works

7.1. iNTRODUCTION

Telecommunications begin with messages that are converted into electronic or optical signals. Some signals, such as those that carry voice or music, are created in an analogue or wave format, but may be converted into a digital or mathematical format for faster and more efficient transmission. The signals are then sent over a medium to a receiver, where they are decoded back into a form that the person receiving the message can understand. There are a variety of ways to create and decode signals, and many different ways to transmit signals.

CREATING AND RECEIVING THE SIGNAL

7.2.1. Telegraph

Devices such as the telegraph and telephone relay messages by creating modulated electrical impulses, or impulses that change in a systematic way. These impulses are then sent along wires, through the air as radio waves, or via other media to a receiver that decodes the modulation. The telegraph, the earliest method of delivering telecommunications, works by converting the contacts (connections between two conductors that permit a flow of current) between a telegraph key and a metal conductor into electrical impulses. These impulses are sent along a wire to a receiver, which converts the impulses into short and long bursts of sound or into dots and dashes on a simple printing device. Specific sequences of dots and dashes represent letters of the alphabet. In the early days of the telegraph, these sequences were decoded by telegraph operators. In this way, telegraph operators could transmit and receive letters that spelled terms. Later versions of the telegraph could decipher letters and numbers automatically. Telegraphs have been largely replaced by other forms of telecommunications, such as electronic mail (e-mail), but they are still used in some parts of the world to send messages.

7.2.2. Telephone

The telephone uses a diaphragm (small membrane) connected to a magnet and a wire coil to convert sound into an analogue or electrical waveform representation of the sound. When a person speaks into the telephones microphone, sound waves created by the voice vibrate the diaphragm, which in turn creates electrical impulses that are sent along a telephone wire. The receivers wire is connected to a speaker, which converts the modulated electrical impulses back into sound.

7.2.3. Radio

Broadcast radio and cellular radio telephones are examples of devices that create signals by modulating radio waves. A radio wave is one type of electromagnetic radiation, a form of energy that travels in waves. Microwaves are also electromagnetic waves, but with shorter wavelengths and higher frequencies. In telecommunications, a transmitter creates and emits radio waves. The transmitter electronically modulates or encodes sound or other information onto the radio waves by varying either the amplitude (height) of the radio waves, or by varying the frequency (number) of the waves within an established range. A receiver (tuner) tuned to a specific frequency or range of frequencies will pick up the modulation added to the radio waves. A speaker connected to the tuner converts the modulation back into sound.

7.2.4. Television

Broadcast television works in a similar fashion. A television camera takes the light reflected from a scene and converts it into an electronic signal, which is transmitted over high-frequency radio waves. A television set contains a tuner that receives the signal and uses that signal to modulate the images seen on the picture tube. The picture tube contains an electron gun that shoots electrons onto a photo-sensitive display screen. The electrons illuminate the screen wherever they fall, thus creating moving pictures.

Telegraphs, telephones, radio, and television all work by modifying electronic signals, making the signals imitate, or reproduce, the original message. This form of transmission is known as analogue transmission. Computers and other types of electronic equipment, however, transmit digital information. Digital technologies convert a message into an electronic or optical form first by measuring different qualities of the message, such as the pitch and volume of a voice, many times. These measurements are then encoded into multiple series of binary numbers, or 1s and 0s. Finally, digital technologies create and send impulses that correspond to the series of 1s and 0s. Digital information can be transmitted faster and more clearly than analogue signals, because the impulses only need to correspond to two digits and not to the full range of qualities that compose the original message, such as the pitch and volume of a human voice. While digital transmissions can be sent over wires, cables or radio waves, they must be decoded by a digital receiver. New digital telephones and televisions are being developed to make telecommunications more efficient.

7.2.5. Computers

Personal computers primarily communicate with each other and with larger networks, such as the Internet, by using the ordinary telephone network. Increasing numbers of computers rely on broadband networks provided by telephone and cable television companies to send text, music, and video over the Internet at high speeds. Since the telephone network functions by converting sound into electronic signals, the computer must first convert its digital data into sound. Computers do this with a device called a modem, which is short for modulator/demodulator. A modem converts the stream of 1s and 0s from a computer into an analogue signal that can then be transmitted over the telephone network, as a speakers voice would. The modem of the receiving computer demodulates the analogue sound signal back into a digital form that the computer can understand.

7.3. TRANSMITTING THE SIGNAL

Telecommunications systems deliver messages using a number of different transmission media, including copper wires, fibre-optic cables, communication satellites, and microwave radio. One way to categorize telecommunications media is to consider whether or not the media uses wires. Wire-based (or wire line) telecommunications provide the initial link between most telephones and the telephone network and are a reliable means for transmitting messages. Telecommunications without wires, commonly referred to as wireless communications, use technologies such as cordless telephones, cellular radio telephones, pagers, and satellites. Wireless communications offer increased mobility and flexibility. In the future some experts believe that wireless devices will also offer high-speed Internet access.

You may want to go back to the key words listed at the beginning of the unit and check that you are familiar with each one. Give their Romanian equivalents (if necessary, you can use the glossary provided at the end of the textbook).

EXERCISES

EXERCISES

A. READING

The purpose of the following exercises is to develop reading strategies and reinforce topic related vocabulary, not to check background knowledge.

A.1. Having read the text, answer the following questions (the specifications in brackets refer to the section in the text where the answer can be found):

1. What is the means of creating a signal in telegraph communications?

2. What is the means of creating a signal in telephone communications?

3. What is the means of creating a signal in radio communications?

4. What is the means of creating a signal in television?

5. What is the means of creating a signal in computer-based?

A.2. Fill in the following table with information about signal manipulation given in the text.

Table 7.1

B. VOCABULARY WORK

The purpose of the following exercises is to promote the acquisition of new lexical items by providing collocations, terms followed by prepositions lexical sets and translations of the terms considered relevant to the topic.

B.1. Match the operation principles described below with the type of telecommunication system in the list.

The earliest method of delivering telecommunications, works by converting the contacts (connections between two conductors that permit a flow of current) between a telegraph key and a metal conductor into electrical impulses. These impulses are sent along a wire to a receiver, which converts the impulses into short and long bursts of sound or into dots and dashes on a simple printing device. Specific sequences of dots and dashes represent letters of the alphabet.

2. The transmitter electronically modulates or encodes sound or other information onto the radio waves by varying either the amplitude (height) of the radio waves, or by varying the frequency (number) of the waves within an established range. A receiver (tuner) tuned to a specific frequency or range of frequencies will pick up the modulation added to the radio waves. A speaker connected to the tuner converts the modulation back into sound.

3. A modem converts the stream of 1s and 0s from a computer into an analogue signal that can then be transmitted over the telephone network, as a speakers voice would. The modem of the receiver demodulates the analogue sound signal back into a digital form.

a. telephone

b. telegraph

c. computer

d. television

e. radio

B.2. In each series of four terms given below there is one term that does not belong in the series. Underline the odd word and justify your decision, as shown in the following example:

e.g.: digital format, mathematical format, transmission, dots and dashes.

1. diaphragm wire coil, cable television companies, cordless telephones.

2. high-speed Internet access, wavelength, frequency, encode.

3. photo-sensitive display screen, analogue transmission, series of binary numbers, contacts.

4. communication satellites,, contacts, telegraph key, metal conductor, electrical impulses.

5. modem, encode, microwave radio, fibre-optic cable.

C. LANGUAGE FOCUS: COMPARISON AND CONTRAST

The purpose of the following exercises is to develop language awareness in terms of expressing comparison and teach contrastive conjunctions.

C.1. Read the sentences below and identify similarities and differences of the things described.

Microwaves are also electromagnetic waves, but with shorter wavelengths and higher frequencies.

2. This form of transmission is known as analogue transmission. Computers and other types of electronic equipment, however, transmit digital information.

3. Digital information can be transmitted faster and more clearly than analogue signals, because the impulses only need to correspond to two digits and not to the full range of qualities that compose the original message, such as the pitch and volume of a human voice.

4. While digital transmissions can be sent over wires, cables or radio waves, they must be decoded by a digital receiver.

Broadcast television works in a similar fashion as radio.

C.2. Identify the terms that render contrastive meaning.

C.3. Complete the list below with other terms with similar meaning.

However, nevertheless, but, on the other hand, despite of, in spite of, regardless of, yet, although, even though, even if, etc.

D. TRANSLATION

The purpose of this exercise is to develop translating skills.

D.1. Translate the following terms into English:

semnal optic

2. demodulare

3. modulare

4. unda radio

5. lungime de unda

6. impuls electric

7. unda electromagnetica

8. microunda

9. medii de transmisie

10. fibra optica

E. SPEAKING

The purpose of these exercises is to develop speaking skills with a focus on

E.1. Choose one of the telecommunications systems described in the text. Work in pairs, comparing the two chosen telecommunications systems using the following patterns.

X is considerably  cheaper/ more efficient THAN Y

very much

quite a lot

rather

somewhat

slightly

scarcely

hardly

only just

X is  exactly  the same as Y

precisely

just

virtually

practically

more or less

almost

nearly

approximately

X is totally different from Y

completely

entirely

quite

X and Y are dissimilar in every respect

different way