Text II Transmitting the Signal

EXERCISE 1

Read and translate the textand say about the way telecommunications systems deliver messages.

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 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.

EXERCISE 2

Insert the missing information.

1. Devices such as the _______relay messages by creating modulated electrical impulses, or impulses that change in a systematic way.

2. In the early days of the telegraph, _______were decoded by telegraph operators.

3. _____ is one type of electromagnetic radiation, a form of energy that travels in waves.

4. These impulses are then sent along____, through the ___as radio waves, or via other ___to a receiver that decodes the modulation.

5. _________works in a similar fashion, as radio and cellular radio telephones.

6. The form of transmission, which works by modifying _____signals, making the signals imitate, or_____, the original message is known as analogtransmission.

7. ____can be transmitted faster and more clearly than analog signals, because the impulses only need to correspond to two ____and not to the full range of qualities that compose the original message, such as the pitch and volume of a human voice.

8. A large number of computers rely on ________provided by telephone and cable television companies to send____, music, and _____over the Internet at high speeds.

9. There are a variety of ways to ____and ____ signals, and many different ways to transmit signals.

UNIT III

TRANSMISSION MEDIA

Text I

Wires and Cables

EXERCISE 1

Read and translate the text

Wires and cables were the original medium for telecommunications and are still the primary means for telephone connections. Wireline transmission evolved from telegraph to telephone service and continues to provide the majority of telecommunications services. Wires connect telephones together within a home or business and also connect these telephones to the nearest telephone switching facility.

Other wireline services employ coaxial cable, which is used by cable television to provide hundreds of video channels to subscribers. Much of the content transmitted by the coaxial cable of cable television systems is sent by satellite to a central location known as the headend. Coaxial cables flow from the headend throughout a community and onward to individual residences and, finally, to individual television sets. Because signals weaken as distance from the headend increases, the coaxial cable network includes amplifiers that process and retransmit the television signals.

EXERCISE 2

Words and expressions to be remembered:

Medium (pl. media) – способ, средство; среда.

switchingfacility – коммутационное оборудование

coaxialcable - коаксиальный кабель ( электрический провод, применяемый в сетях, имеющий соосное (коаксиальное) расположение центрального проводника, окруженного изолятором, и внешнего проводника, выполненного в виде проволочной оплетки; снаружи покрыт еще одним защитным слоем изолятора; менее подвержен помехам и ослаблению сигнала по сравнению с другими типами кабеля )

wires – провода

cable - кабель

headend – головной узел (в компьютерной сети)

amplifier – усилитель

Cordless telephones = wireless telephones

bentpipes - коленчатые трубы

relay – радиорелейная

EXERCISE 3

Match the following phrases with their Russian meanings:

fiber-optic hair-thin strands "backbone" link AM (amplitude modulation) FM (frequency modulation) high-capacity links Communications satellites orbit geostationary geosynchronous orbit scatter

спутники связи; амплитудная модуляция; магистральная линия связи; магистральный канал связи; геосинхронная орбита; частотная модуляция; двигаться или вращаться по орбите распылять, рассеивать; жила (кабеля) толщиною с волос; высокоэффективные связи; геостационарный; волоконно-оптический, оптоволоконный;

EXERCISE 4

Make up your own sentences with the word combinations and phrases from exercise 2

EXERCISE 5

Answer the questions

1. What was the original medium for telecommunications?

2. What is still the primary means for telephone connections?

3. What did the Wireline transmission start from?

4. What is the main purpose of coaxial cable?