Complete the following sentences. Use the words from the texts.

 

discovery	included	began signal
challenge	to carry	transmit	telegraph
History of Telecommunications.
Communicating over	long distances has been a		. throughout
history. In ancient times,	runners were	used		important messages

 

between rulers or other important people. Other forms of long-distance communication smoke signals, chains of searchlights and flags to send a

message from one tower to another, carrier pigeons, and horses. Modern

telecommunications	with the discovery that electricity can be used to
	a signal. For the first time, a	could be sent faster than any other

 

mode of transportation. The first practical telecommunications device to make use of this was the

 

6. Read, translate the text and give the summary of each paragraph.

 

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, walkie-talkies, citizens band (CB) radios, pagers, and satellites. Wireless communications offer increased mobility and flexibility.

 

Wires and cables were the original medium for telecommunications and are still the primary means for telephone connections. Wire line 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 wire line 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.

 

Fiber-optic cables are cables made of specially treated glass that can transmit signals in the form of pulsed beams of laser light. Fiber-optic cables cany many times more information than copper wires can, and are able to transmit several television channels or thousands of telephone conversations at the same time. Fiber-optic technology is being used to replace copper wires in transoceanic cables and cables in other areas where large amounts of data are sent. New improvements promise cables that can transmit millions of telephone calls over a single fiber.

 

Wireless telecommunications use radio waves, sent through space from one antenna to another, as the medium for communication. Radio waves are used for receiving AM and FM radio and for receiving television. Cordless telephones and wireless radio telephone services, such as cellular radio telephones and pagers, also use radio waves. Telephone companies use microwaves to send signals over long distances. Microwaves use higher frequencies than the radio waves used for AM, FM, or cellular telephone transmissions and they can transmit larger amounts of data more efficiently. Microwaves have characteristics similar to those of light waves, and transmit pencil-thin beams that can be received using dish-shaped antennas. Such narrow beams can be focused to a particular destination and provide reliable transmissions over short distances on earth. Even higher and narrower beams provide the high-capacity links to and from satellites. The high frequencies easily penetrate the ionosphere (a layer of the earth's atmosphere that blocks low-frequency waves) and provide a high-quality signal.

 

Communications satellites provide a means of transmitting telecommunications all over the globe, without the need for a network of wires and cables. They orbit the earth at a speed that allows them to stay above the same place on the earth at all times. This type of orbit is called geostationary orbit. The satellites receive transmissions from earth and transmit them back to numerous earth station receivers scattered within the receiving coverage area of

 

 

the satellite. This relay function makes it possible for satellites to operate as «bent pipes», that is, wireless transfer stations for point-to-point and point-to-multipoint transmissions. Communications satellites are used by telephone and television companies to transmit signals across great distances. Ship, airplane, and land navigators also receive signals from satellites to determine geographic positions.

 

 

7. Cheek yourself. Answer the following questions.

 

1) What do telecommunications mean?

 

2) What are telecommunications used for?

 

3) How can telecommunications messages be sent?

 

4) What is wire line transmission?

 

7) How does broadcast television work?

 

8) Can you explain the difference between analog and digital transmission?

 

9) What makes telecommunications more efficient?

 

10) What devices convert digits into sound?

 

11) What kinds of transmission media do you know?

 

12) What do you know about the history of telecommunications?

 

 

Unit 8. NETWORKS

 

Warm-up

 

1. What is a network?

 

2. What are networks created for?

 

Reading

 

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