TEXT 2. Signal Transmission

11. Выучите следующие слова и выражения:

transfer [træns'fɜ:] - переносить, перемещать

amplify ['æmplɪfaɪ] - усиливать

transduction [træns'dʌkʃn] - преобразование

transducer [trænz'djuːsə ], [trɑːn-] - преобразователь; датчик; приёмник

vary ['vɛərɪ] - меняться, изменяться; отличаться

convert [kən'vɜːt] - преобразовывать; превращать

AD converter - аналого-цифровой преобразователь, АЦП

DA converter - цифро-аналоговый преобразователь, ЦАП

shielding - экранирование (способ защиты передающей среды от электро-магнитных помех)

cable ['keɪbl] – кабель

coaxial cable [ˌkəu'æksɪəl] - коаксиальный кабель

twisted pair cable - кабель с витыми жилами, скрученная пара

diminish [dɪ'mɪnɪʃ] уменьшаться, уменьшать

convey [kən'veɪ] передавать

transition [træn'zɪʃ(ə)n ],[ træn'sɪʒ(ə)n] перемещение, переход

digitization ['dɪʤɪtaɪzeɪʃ(ə)n] дискретизация, оцифровка, преобразование в цифровую форму

quantization [ˌkwɔntaɪ'zeɪʃ(ə)n] - квантование (преобразование непрерывной информации в дискретную)

bounded – ограниченный

guided - направляемый

jacket - оболочка (кабеля)

optical fiber (=fibre) [faɪbə] - оптическое волокно; световод, светопровод

induce [ɪn'djuːs] – вызывать; индуцировать

simplex - односторонняя связь

half-duplex [hɑːf'djuːpleks] - полудуплексная связь, поочерёдная двусторонняя связь

full duplex - дуплексная связь, одновременная двусторонняя связь, дуплекс

multiplex [mʌlti pleks] мультиплексная передача

12. Прочитайте и устно переведите текст:

As mentioned above, information can be transferred in two forms, analog and digital. An analog format is that in which information is transmitted by modulating a continuous transmission signal, such as amplifying a signal's strength or varying its frequency to add or take away data. For example, telephones take sound vibrations and turn them into electrical vibrations of the same shape before they are transmitted over traditional telephone lines. The process of changing energy from one form into another is called transduction. Some common examples of transducers are a microphone which converts sound into an electrical signal, or an antenna which converts electromagnetic waves into electric current and vice versa.

The main merit of an analog signal is its fine definition. However, its primary disadvantage is that any system has noise – i.e., random unwanted variation leading to signal loss and distortion. Electrically, these effects of noise can be diminished by shielding, good connections, and several cable types such as coaxial or twisted pair. Other methods of conveying an analog signal are to use modulation or to change the phase of the base signal.

In contrast to analog communications, digital communications are the transfer of discrete messages. These messages may be digital (when originating from a data source, for example, a computer) or may start out as analog, being then converted to digital for modulation, converted back to analog for radio frequency transmission and, finally, converted to digital again. The conversion from the “real world” analog signal to its discretized digital counterpart is called analog-to-digital (AD) conversion. Analogously, a transition in the opposite direction is shorthanded as DA conversion.

A digitization process carried out by an AD converter (ADC) is broken into two stages. The first stage is sampling by which a continuous-time signal is “reduced” to a discrete-time sequence. At the second stage, the ADC converts the continuous range of values to the finite set of discrete values by rounding the input values to the nearest integer numbers. This process known as quantization usually results in deviations from the theoretically perfect reconstruction capabilities, collectively referred to as distortion.

The type of a signal, analog or discrete, used for communications depends on how far the signal has to travel and the medium it will have to pass through. In telecommunications, transmission media are classified into two categories: bounded, or guided media, and wireless, or unguided media. In both cases, communication is in the form of electromagnetic waves.

Bounded media are physical links through which signals are confined to a narrow path and energy waves are guided along a solid medium. Bounded media are made up of an external conductor (usually copper) bounded by jacket material. Three common types of bounded media are twisted pair cables, coaxial cables, and optical fibers. Plain wires can be used, but they are generally unreliable in screening out noise and are rarely considered.

Wireless transmission requires no physical means to define the path a transmitted signal takes. Instead, the waves radiate by inducing a current in a transmitting antenna and then travel through the air or free space. Examples of these media include microwave, radio and satellite transmission.

Any transmission may be simplex, half-duplex, or full-duplex. In simplex transmission, signals are transmitted in only one direction; one station is a transmitter and the other is the receiver. In half-duplex operation, both stations may transmit, but only one at a time. In full duplex operation, both stations may transmit simultaneously. Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and to share the same physical channel are called multiplex systems.

13. Ознакомьтесь с дополнительными словами и выражениями:

merit ['merɪt] достоинство

counterpart ['kauntəpɑ:t] - дубликат, копия, двойник, аналог

confine ['kɔnfaɪn] – (n) граница

(v) [kən'faɪn] – ограничивать

shorthand – стенография; условное обозначение

deviation [ˌdiːvɪ'eɪʃ(ə)n] – отклонение

simultaneous [ˌsɪm(ə)l'teɪnɪəs] - одновременный, синхронный

14. Ответьте на вопросы, используя информацию текста:

1. How is information transmitted in an analog format? 2. What is transduction? 3. What transducers do you know? 4. What are the advantages and disadvantages od analog transmission? 5. Are there any ways to reduce noise in analog signal transmission? 6. What is AD conversion used for? 7. What does a digitization process consist of? 8. What are bounded media? 9. How can wireless transmission be described? 10. How are telecommuncations classified depending on the number of transmitters and receivers and the direction of simultaneous transmission?

15. Найдите в тексте слова и выражения, эквивалентные данным ниже:

Усиливать сигнал; сообщение; изменять частоту; источник; выпадение сигнала; уменьшать; экранирование; исходный сигнал; передача дискретных сообщений; округлять исходные величины; целое число; оцифровка; квантование; внешний проводник; обычные провода; отслеживать шум.

16. Переведите на русский язык следующие словосочетания:

Continuous transmission signal; sound vibrations; fine definition; random unwanted variation; theoretically perfect reconstruction; bounded by jacket material; simplex transmission; full-duplex operation; multiplex systems.

17. Вставьте пропущенные предлоги:

1. Information can be transferred … two forms. 2. Telephones take sound vibrations and turn them … electrical vibrations … the same shape. 3. Noise in a sommunications system is understood as random unwanted variation leading … signal loss and distortion. 4. In contrast … analog communications, digital communications are the transfer of discrete messages. 5. A digitization process carried … by an AD converter is broken into two stages. 6. In bounded media energy waves are guided … a solid medium. 7. In the half-duplex operation, both stations may transmit, but only one... a time.

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