Creating and receiving the signal

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 words. 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.

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

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 (see Frequency Modulation). 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.

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 analogtransmission. 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 analog 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.

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 analog signal that can then be transmitted over the telephone network, as a speaker’s voice would. The modem of the receiving computer demodulates the analog sound signal back into a digital form that the computer can understand.

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 analog 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.

______________________

signals - сигналы

be converted (into ) – быть преобразованным

be decoded - быть расшифрованным

to create – создавать

receive - получить

transmit - передать

GRAMMAR EXERCISES

I. Translate the following sentences, pay attention to the Modal Verbs and their equivalents.

1. The designers can always improve the operation of these receivers. 2. He could use any transmitter for this system. 3. The scientists are able to construct a new device by using semiconductors. 4. The designer was able to construct a new device by using semiconductors. 5. The engineers must test a new receiver for using it in this system. 6. We have to increase the current strength by decreasing the resistance of the circuit. 7. For improving the system operation the designer was to use low weight equipment. 8. Because of the electrical neutrality requirement, the space charge is to remain constant. 9. The engineers were to investigate new means of radio communication. 10. After finishing of the experiment the scientists will have to discuss the results. 11. The students did not have to conduct experiments in this field of science. 12. They did not have to analyze these data. 13. We may say that photoelectric properties of transistor are largely used in TV sets. 14. The students might use all the laboratory equipment. 15. The students were allowed to show all the automatic devices. 16. The students will be allowed to conduct this experiment in the laboratory.

II. Translate the following sentences and explain the using of the Modals.

1. Can you tell me the time? 2. Can you speak English? 3. You can take this picture if you like it. 4. He can hardly have meant that. 5. He was not able to get there in time. 6. I shall be able to come on Saturday. 7. May I ask a question? 8. Maybe he will help you. 9. I put on my raincoat because I thought it might rain. 10. Smoking is not allowed here. 11. I am afraid the teacher will not allow me to rewrite the composition. 12. I must get up early every day. 13. He must be ill. 14. He must be somewhere here.

III. Translate into Russian the following text and find the Predicates in Passive.

TRANSMITTING THE SIGNAL

Telecommunications systems deliver messages using a number of different transmission media, including copper wires, fiber-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 wireline) 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.

IV. Translate the following sentences, pay attention to the translation of “should, would, could, might + Infinitive”.

1. Without electronic equipment space flights would be impossible. 2. It is required that natural piezo [pai’izou] electric crystals of quartz should be used in radio broadcasting transmitters. 3. Without quantum electronics these instruments could not be developed. 4. Modern complex controls can perform functions which man would not be able to carry out. 5. The engineer suggested this photographic cell should be used for measuring temperature. 6. Everything might have been solved long ago.

LEXICAL EXERCISES

V. Translate the following sentences, pay attention to the constructions “as high as, as low as” – до (перед цифрами).

1. In the chemical reaction the temperature of gases may be as high as 3 500° Centigrade. 2. The voltage dropped to as low as 25 volts. 3. The possibility of discharge large amounts of energy was demonstrated as early as 1919 by Rutherford. 4. The planet Pluto was discovered as recently as 1930.

VI. Translate the following terms

(adverb + participle I or adjective + noun)

Pattern:directly fed antenna

↓

Какая? ← антенна

↓

Питаемая

↓

Непосредственно

Русский термин: антенна с непосредственным питанием.

1. continuously adjustable capacitor

2. electronically controlled filter

3. remotely controlled plant

4. periodically operated switch

5. horizontally polarized antenna

6. aerodynamically supported missile

7. continuously measuring control system

VII. Form verbs using the suffixes and translate them into Russian.

-en:length, strength, light, wid(e), broad, bright, hard

-ify:solid, pur(e), simpl(e), intens(e), electr(ic), qual(ity)

-ize:magnet, revolution, organ, crystal, character

GRAMMAR REFERENCES

МОДАЛЬНЫЕ ГЛАГОЛЫ (Modal Verbs) и их особенности

Модальные глаголы обозначают не само действие, а указывают на отношение к нему говорящего лица. Модальные глаголы can, may, must выражают способность, возможность, допустимость, долженствование.

Модальные глаголы употребляются только в сочетании с инфинитивом смыслового глагола без частицы to. Эти глаголы часто называют недостаточными, так как они:

1. Не имеют неличных форм — инфинитива, причастия, герундия.

2. Не изменяются ни по лицам, ни по числам (не имеют окончания в 3-м лице единственного числа).

3. Образуют вопросительную форму путем постановки глаголов can, must или may перед подлежащим, а отрицательную форму — путем добавления отрицания not.

Для выражения необходимости, допустимости, способности выполнения какого-нибудь действия после подлежащего ставится модальный глагол can, may или must, затем смысловой глагол в первой форме.

Can

S + May + V

Must

/ can carry out this experiment alone.

Я могупровести этот эксперимент самостоятельно

They maycome into the room.

Они могутзайти в комнату.

Kate must read this article.

Катя должнапрочитать эту статью.

Глагол can (could)

Глагол имеет две формы: настоящее время сап и прошедшее время could. Глагол выражает

физическую, умственную способность, умение или возможность выполнения действия.

Употребление глагола can (could) наглядно показано в таблице.

Случаи употребления глагола can (could)

1. Для выражения They can read this text Они могут читать этот текст.

возможности или способности

совершить действие

(с Indefinite Infinitive)

2. Для выражения удивления, She cannot think so. Не может быть, чтобы она думала сомнения по поводу так.
возможности совершения
действия:

а) в настоящем или будущем Can they receive this Неужели они получат это письмо времени (с Indefinite Infinitive) letter tomorrow? завтра?

б) в прошлом (с Perfect He cannot have thought Не может быть, чтобы он Infinitive). about it. думал об этом.

3. Для выражения They could laugh when Они могли смеяться когда возможности или способности they were happy. были счастливы.
совершить действие

в прошлом (с Indefinite Infinitive)

4. В главной части условных
предложений:

а) в условных предложенияхвторого If he knew he could Если бы он знал,

типа (с Indefinite Infinitive) answer. он мог бы ответить

б) в условных предложениях If she had come she could Если бы она приехала,

третьего типа (с Perfect. have taken it. она смогла бы взять это.

Infinitive)

Глагол may (might)

Глагол may имеет две формы: настоящее время may и прошедшее время might. Чаще всего выражает разрешение, предположение (с оттенком сомнения) или допускаемую возможность совершения действия в любом времени (будущем, настоящем и прошедшем). Употребление глагола may (might) наглядно показано в таблице

1.для выражения разрешения (с Indefinite Infinitive)	You may read now.	Вы можете читать сейчас.
2. Для выражения предположения: а) относящегося к настоящему или будущему (с Indefinite Infinitive) б) относящегося к прошедшему (с Perfect Infinitive)	She may play the piano now. John may miss his lessons tomorrow. She may have received this letter.	Она, возможно, играет на пианино сейчас. Джон, возможно, пропустит занятие завтра. Она, возможно, получила это письмо.
3. В придаточных предложениях цели (с Indefinite Infinitive)	He will take my dictionary so that she may translate the text.	Он возьмет мой словарь, чтобы она могла перевести, текст.
4. Для выражения предположения, относящегося к настоящему или будущему (с Indefinite infinitive)	She might play the piano now. John might miss his lessons tomorrow.	Она, может быть, играет сейчас на пианино. Джон, может быть, и пропустит занятия завтра.
4. В главной части условных предложений: а) в условных предложениях второго типа (с Indefinite Infinitive) б) в условных предложениях третьего типа (с Perfect Infinitive)	If he knew, he might come to Kiev If they had wanted, they might have carried out this experiment.	Если бы он знал, он мог бы приехать в Киев. Если бы они захотели, они могли бы провести этот эксперимент.