Signals of the Television System
Special signals are sent out by the television transmitter in addition to the picture impulses. These special signals have the purpose of synchronizing the picture at the receiver with the picture that is picked up by the camera.
At the television receiver, the picture and audio signals are picked up simultaneously by a single antenna. The voltages induced in the receiving antenna are fed into the radio frequency stage of the receiver; and the picture carrier and the sound carrier are converted by superheterodyne conversion method into two separate intermediate frequency signals. One signal corresponds to the sound carrier and the other — to the video or picture carrier. Two separate intermediate frequency amplifier channels are employed, one for the picture signal and the other for the sound signal. The sound intermediate frequency signal is demodulated by a detector. After sufficient amplification by the audio amplifier, the sound signal is reproduced by the loudspeaker in the usual way.
The picture intermediate frequency signal is amplified by several stages having wide-band frequency characteristics and is then fed into the video (picture) detector, where the intermediate frequency signal is then demodulated in the same manner as in an ordinary sound receiver. The video (picture) signal which appears in the output of the detector is then amplified in a video amplifier, which corresponds to the audio amplifier in a sound receiver, except that it must pass a much wider range of frequencies.
In place of the loudspeaker used in the sound system, a device is used which converts the varying amplitude of the video signals into corresponding variations of light.
УРОК 3
МОДАЛЬНЫЕ ГЛАГОЛЫ И ИХ ЭКВИВАЛЕНТЫ
Особенности модальных глаголов:
1. Обозначают не действие, а отношение к действию.
2. Не имеют окончания –s в третьем лице ед.ч. настоящего времени группы Indefinite.
3. В предложении выполняют функцию вспомогательного глагола.
4. Следующий за ними смысловой глагол употребляется без частицы to.
5. Не имеют неличных форм (инфинитива, герундия, причастия), употребляются только в двух временных формах: Present Indefinite, Past Indefinite, глагол must – только в Present Indefinite.
| Глагол | Эквивалент | Перевод | Примеры |
| Can (could) | to be able to | мочь, уметь, быть в состоянии | This device can mea- sure currents. The engineer will be able to find practical application of this circuits. |
| May (might) | to be allowed to to be permitted to | мочь, быть позволенным (допустимость дей- ствия) | The engineer may change this design. The engineer will be allowed to change this design. |
| Must | to have to to be to should ought to need not | должен вынужден, прихо- дится (по обстоя- тельствам) должен ( по плану) следует, следовало бы не нужно | The students must conduct these expe- riments in time. The scientists had to solve many prob- lems The students were to compare the currents. You should be more attentive when you carry out the experi- ment. They need not use all the equipment. |
ПРЕДТЕКСТОВЫЕ УПРАЖНЕНИЯ
I. Прочтите и переведите предложения, содержащие модальные глаголы и их эквиваленты:
1. The designers can always improve the operationof these receivers.
2. He could use any transmitter for this system.
3. The scientists are able to perfect this system operation due to the application of superconducting materials.
4. The designer was able to construct a new deviceby 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 finishingthe experiment the scientistswill have to discuss the results.
11. The students didn't have to conduct experiments in this field of science.
12. They didn't have to analyse these data.
13. We may say that photoelectric properties of transistors 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. Прочтите и переведите предложения, обращая внимание на способы перевода инфинитива в страдательном залоге после модальных глаголов и их эквивалентов:
1. Electrolysis may be defined as a process by which a chemical reaction is carried out.
2. The mass may often be defined as the quantity of matter remaining constant everywhere.
3. When the forces act in the same direction, the resultant can be found by adding the applied forces.
4. The energy which has to be supplied by the generatororbattery is transformed into heat within the conductor.
5. The frequency of an oscillator is to be kept constant by means of an oscillating crystal.
6. To detect very weak radio signals a directional antenna and a highly sensitive radio receiver are to be used.
7. A number of scientific problems were to be solved in connection with the construction of a network of electrotransmission lines.
III. Прочтите предложения, определив функцию причастия II, и переведите предложения:
1. The oscillations produced in the antenna are weak.
2. The antenna receives only a small part of energyradiated by the transmitter.
3. Negatively charged ions are attracted to theanode; positively charged ions are attracted to the cathode.
4. The results obtained are of great importance.
5. The constructed transmitter operated onvarious frequencies.
6. If arranged according to their atomic weights, the elements show the periodicity of their properties.
7. When heated, magnetized steel will lose its magnetism.
8. When produced in one tube, minimum grid voltage is produced in the other tube.
9. Placed in a different surrounding medium the device operates differently.
TEXT
CONVERTERS
1. А unique approach for converting heat directly into electricity is the nuclear thermionic converter. 2. Such converters consist of a heated emitter of electrons, a collector, and a gas (that becomes a plasma when ionized) between the electrodes. 3. The main problem with conventional converters is that the gas used is highly corrosive. 4. Also, this gas tends to make the passage of electrons difficult. 5. One of the American laboratories has produced a nuclear converter that eliminates these drawbacks. 6. In this converter, uranium is used in the emitter. 7. When bombarded by neutrons from a reactor, the uranium undergoes fission. 8. As a result, the high-energy particles heat the emitter to a much lower temperature than in other converters and, at the same time, produce the plasma by ionizing the gas. 9. Electrons have to flow readily from the emitter to the collector of the unit.
10. The development of a cell which has to convert nuclear energy directly into electricity has been made by General Motors. 11. It is called a liquid metal cell, and it may produce energy by collecting the electrical charges given off by the reaction of one liquid metal with another — in contrast with conventional storage batteries whose energy is produced by the action of acid upon the metal. 12. The cell is able to produce a larger proportion of its full theoretical power than normal storage batteries due to the greater conductivity of its molten1 salt electrolyte and the quicker reaction rates of the metals with salts. 13. A liquid metal cell in the form of a one-foot cube can produce 11 kilowatts compared with 11/2 kilowatts obtainable from storage batteries of the same dimensions. 14. In converting nuclear energy to electricity the cell has to form a part of a regenerative cycle which can work for long periods using the heat of a nuclear reactor. 15. The heat of the reactor separates the metals since their melting points differ appreciably. 16. When the metals recombine in the cell, a reaction occurs producing an electric current. 17. As heating is continued the system will produce electricity. 18. A cell of this type operates continuously for 60 hours.
Пояснение к тексту
1. molten — расплавленный
Слова для запоминания
п acid, approach, cell, dimension, drawback, fission, passage, storage battery
v approach, convert, eliminate, give off, separate, undergo (underwent, undergone)
a obtainable, separate, unique
prep since
cj since
Слова для повторения
n unit
v compare, differ
ado continuously, readily
УПРАЖНЕНИЯ
IV. Прочтите предложения, замените модальный глагол соответствующим эквивалентом из двух, данных в скобках, и переведите предложения:
1. The scientistsmust separate these fission products (are able to, have to).
2. The designer canchange the dimension of this cell (is able to, is to).
3. The students can obtain interesting data on waves travelling (are able to, are to).
4. Electronsmust flow fromthe emitterto the collector ofthe unit (are allowed to, have to).
5. This cell could convert nuclear energy directly into electricity (was to, was able to).
6. This plant must produce 4 million TV sets (is to, is able to).
7. The cell can work for long periods using the heat of a nuclear reactor (has to, is able to).
V. Прочтите и переведите предложения, обращая внимание на способы перевода причастия II:
1. The operation of the receiving stationinfluenced by a number of factors was discussed by engineers.
2. The generation of electricity from magnetism dealt with by Faraday was a very important scientific discovery.
3. The work of Rutherford followed by great research work of other scientists was of great help for understanding many natural phenomena.
4. Gagarin's first space flight followed by manyothers wasvery important for the development of astronautics.
5. Molecules of even a good insulator acted upon byan electric field produce a motion of electrons due to the field.
6. Some drawbacks of the reactor referred to in this article will be eliminated.
7. The dimensions of the body referred to in that text-book will be used in our experiment.
VI. * Прочтите предложения, определив функции выделенных слов, и переведите предложения:
1. The indications obtained increased with the voltageinduced.
2. The experimentcarried out resulted in the improvement of all parts of the system.
3. Whenused in this medium the transmitteroperated successfully.
4. By collecting the electrical chargesreleased by the reaction of one liquid metal with another the cellproduced energy.
5. The scientistscompared the resultsobtained by various laboratory-assistants.
6. Some convertersused the energyreleased from fission.
7. Analysis showed that the speed of conversion depended on many factors.
8. The capsuleseparated landed successfully in a given region.
VII. * Укажите дробью синонимы: к каждому слову из левов колонки (числитель) подберите его синоним из правой (знаменатель):
| 1. to permit 2. a dimension 3. a splitting 4. to undergo 5. appreciably 6. to separate 7. to distinguish 8. continuously 9. a drawback 10. main 11. to convert 12. conventional 13. to exclude 14. readily 15. capable 16. to occur |
| 1. usual 2. to eliminate 3. easily 4. able 5. to takeplace 6. constantly 7. to differ 8. a fission 9. to allow 10. to transform 11. to subject 12. a defect 13. considerably 14. a size 15. to isolate 16. chief |
VIII. * Прочтите и переведите сочетания слов:
1. a strong acid; 2. great dimensions; 3. a small storage battery; 4. to undergo fission; 5. unique properties of the cell; 6. given off energy; 7. a scientific approach; 8. a powerful converter; 9. the main drawback; 10. the eliminated drawback; 11. storage battery properties; 12. readily reacting with an acid
IX. Переведите, не пользуясь словарем:
Electrolysis
Electrolysis is a process by which a chemical reaction is carried out by means of the passage of an electric current. The electrical energy enters and leaves the electrolytic medium through electrodes, which ordinarily are pieces1 of metal. The electrode where electrons enter the solution is the cathode; the electrode where the electrons leave is the anode. Negatively charged ions (anions) are attracted to the anode; positively charged ions (cations) are attracted to the cathode.
The process is generally used as a method of depositing2 metals from solution.
The relation between the quantity of material undergoing reaction and the quantity of electricity usedin this reaction was discovered by Faraday.
Пояснения к тексту
1. pieces— кусочки
2. depositing—осаждения, выделения
X. Переведите, пользуясь словарем:
Control Systems
Electronics is being used more and more to control industrial processes, particularly where the speed of a motor has to be accurately controlled. One big advantage is that valves, unlike relays, have no moving parts, no contacts to shatter or burn, and practically no inertia; and their speed of operation is very much greater. Two special types of valves, known as "thyrotrons" and "ignitrons" are generally used for motor control.
A thyrotron is a gas-filled triode, whose gas ionizes when the grid voltage rises above a certain value. "Ionization" is a scientific term for "knocking spots off atoms". An atom consists roughly of a positive nucleus at the centre with a number of negative electrons around it. It is electrically neutral, because the positive nucleus balances the negative electrons. But if an atom loses an electron, this balance no longer holds, and it becomes positively charged. It is then known as a "positive ion."
In the thyrotron, an electron emitted from the hot cathode collides with a gas molecule and we have two free electrons and a positive ion; all tend to collide with other gas molecules. These chain effects soon fill the tube with positive ions which make nice conductors, and a current can flow between cathode and anode. Neon lamps, mercury and sodium vapour street lamps and fluorescent tubes are examples of ionization.
Unlike hard valves, a thyrotron once conducting cannot be cut off by reducing the grid voltage alone, it is necessary to drop or remove the anode supply voltage in order to allow the valve to deionize. It has one great advantage, however, in that it can handle very much larger currents, than vacuum valves. This is why it is used for motor control.
УРОК 4