DATA TRANSMISSION AND COMPUTER NETWORKS

DATA TRANSMISSION AND COMPUTER NETWORKS

AIM:

To recognize the English technical terms related to data transmission and computer networks;

OBJECTIVES:

On successfully completing this unit the student should be able to:

identify correctly the terms defining radio-, television-, and computer technology;

recognise the specific terms related to GPS and GLONASS networks;

describe the functions performed by specialized equipment;

identify the types of equipment used for data transmission and its operation principles;

describe the different types of networks;

assimilate at least 30 terms specific of data transmission within telecommunications networks.

KEY TERMS:

preset frequency, commercial broadcasts, within range, powerful transmitter, shortwave radio, electrically charged layer, commercial television, very high frequency (VHF) radio waves, ultrahigh frequency (UHF) radio waves, teleconferencing, videophones, video camera, private or public television, terrestrial links, scrambled signal, unscrambled signal, network operator, European Phase Alternative Line standard, high-resolution picture, sound quality, aspect ratio, Global Positioning System (GPS), Global Orbiting Navigation Satellite System (GLONASS), positioning information, GPS receiver, process of triangulation, military use, navigational tool, road maps, graphical information, GPS location data, audio services, video services, text services, software services, multimedia services, Integrated Services Digital Network (ISDN), Digital Subscriber Lines (DSL), upgrade, high-speed data transmission, cable modem service, electronic mail (e-mail), text-based message delivery system, automated banking terminals, credit card transactions.

DATA TRANSMISSION AND COMPUTER NETWORKS

1. RADIO-, TV COMMUNICATIONS

1.1. Radio

Radios transmit and receive communications at various preset frequencies. Radio waves carry the signals heard on AM and FM radio, as well as the signals seen on a television set receiving broadcasts from an antenna. Radio is used mostly as a public medium, sending commercial broadcasts from a transmitter to anyone with a radio receiver within its range, so it is known as a point-to-multipoint medium. However, radio can also be used for private point-to-point transmissions. Two-way radios, cordless telephones, and cellular radio telephones are common examples of transceivers, which are devices that can both transmit and receive point-to-point messages.

Personal radio communication is generally limited to short distances (usually a few kilometres), but powerful transmitters can send broadcast radio signals hundreds of kilometres. Shortwave radio, popular with amateur radio enthusiasts, uses a range of radio frequencies that are able to bounce off the ionosphere. This electrically charged layer of the atmosphere reflects certain frequencies of radio waves, such as shortwave frequencies, while allowing higher-frequency waves, such as microwaves, to pass through it. Amateur radio operators use the ionosphere to bounce their radio signals to other radio operators thousands of kilometres away.

1.2. Television

Television is primarily a public broadcasting medium, using point-to-multipoint technology that is broadcast to any user within range of the transmitter. Televisions transmit news and information, as well as entertainment. Commercial television is broadcast over very high frequency (VHF) and ultrahigh frequency (UHF) radio waves and can be received by any television set within range of the transmitter. Televisions have also been used for point-to-point, two-way telecommunications. Teleconferencing, in which a television picture links two physically separated parties, is a convenient way for businesspeople to meet and communicate without the expense or inconvenience of travel. Video cameras on computers now allow personal computer users to teleconference over the Internet. Videophones, which use tiny video cameras and rely on satellite technology, can also send private or public television images and have been used in news reporting in remote locations.

Cable television is a commercial service that links televisions to a source of many different types of video programming using coaxial cable. The cable provider obtains coded, or scrambled, programming from a communications satellite, as well as from terrestrial links, including broadcast television stations. The signal may be scrambled to prevent unpaid access to the programming. The cable provider electronically unscrambles the signal and supplies the decoded signals by cable to subscribers. Television users with personal satellite dishes can access satellite programming directly without a cable installation. Personal satellite dishes are also a subscriber service. Fees are paid to the network operator in return for access to the satellite channels.

Most television sets outside of the United States that receive programming use different types of standards for receiving video signals. The European Phase Alternative Line standard generates a higher-resolution picture than the sets used in the United States, but these television sets are more expensive. Manufacturers now offer digital video and audio signal processing, which features even higher picture resolution and sound quality. The shape of the television screen is changing as well, reflecting the aspect ratio (ratio of image height to width) used for movie presentation.

2. DIGITAL COMMUNICATION NETWORKS

2.1. Global Positioning and Navigation Systems

The United States Global Positioning System (GPS) and the Russian Global Orbiting Navigation Satellite System (GLONASS) are networks of satellites that provide highly accurate positioning information from anywhere on Earth. Both systems use a group of satellites that orbit around the north and south poles at an altitude of 17,500 km (10,900 mi). These satellites constantly broadcast the time and their location above Earth. A GPS receiver picks up broadcasts from these satellites and determines its position through the process of triangulation. Using the time information from each satellite, the receiver calculates the time the signal takes to reach it. Factoring in this time with the speed at which radio signals travel, the receiver calculates its distance from the satellite. Finally, using the location of three satellites and its distance from each satellite, the receiver determines its position.

GPS services, originally designed for military use, are now available to civilians. Handheld GPS receivers allow users to pinpoint their location on Earth to within a few meters. One type of navigational tool used in automobiles integrates a GPS receiver with an intelligent compact disc player capable of displaying road maps and other graphical information. Upon receiving the GPS location data, the CD player can pinpoint the location visually on one of the road maps contained on disc.

2.2. Personal Computers

Personal computers use telecommunications to provide a transmission link for the delivery of audio, video, text, software, and multimedia services. Many experts believe that the convergence of these services will generate consumer demand for new generations of high-speed, broadband networks. Currently, the delivery of most of these audio, video, and text services occurs over existing telephone connections using the Internet. Some computers connect directly to the digital portion of the telephone network using the Integrated Services Digital Network (ISDN) or Digital Subscriber Lines (DSL), but this requires special equipment at user locations. Telephone and cable television companies must also make upgrades to their lines so that they can handle high-speed data transmission. In many locations companies and individuals with high-speed data requirements now have the option of securing DSL service from telephone companies and cable modem service from cable television companies.

Electronic mail, or e-mail, is a key attraction of the Internet and a common form of computer telecommunications. E-mail is a text-based message delivery system that allows information such as typed messages and multimedia to be sent to individual computer users. Local e-mail messages (within a building or a company) typically reach addressees by travelling through wire-based internal networks. E-mail that must travel across town or across a country to reach the final destination usually travels through the telephone network. Other computer telecommunications technologies that businesses frequently use include automated banking terminals and devices for credit card transactions that bill charges directly to a customers bank account.

	You may want to go back to the key words listed at the beginning of the unit and check that you are familiar with each one. Give their Romanian equivalents (if necessary, you can use the glossary provided at the end of the textbook).

EXERCISES

A. READING

The purpose of the following exercises is to develop reading strategies and reinforce topic related vocabulary, not to check background knowledge.

A.1. Re-read section 1. and 2.2. and decide on the uses of these types of communications:

1. Radio

2. Television

3. Computers

A.2. In 2.1. of the text the operation principles of GPS and GLONASS are described. Explain the applications that these systems are most suitable for.

B. VOCABULARY WORK

The purpose of the following exercises is to promote the acquisition of new lexical items by providing collocations, terms followed by prepositions lexical sets and translations of the terms considered relevant to the topic.

B.1. Enter in the following table information related to television (see 1.2):

B.2. Add three more terms to the following lists:

two-way radios, cordless telephones, cellular radio telephones;

very high frequency (VHF), two-way telecommunications, videophones;

satellite, receiver, calculate;

B.3. Fill in the missing terms:

1. The _______________(GPS) and the _____________(GLONASS) are networks of satellites that provide highly accurate positioning information from anywhere on Earth.

2. Both systems use a group of ________that _________ around the north and south poles at a _____________of 17,500 km (10,900 mi).

3. Handheld GPS _________allow users to _________their location on Earth to within a few meters.

4. Some computers connect directly to the digital portion of the telephone network using the _________________(ISDN) or ______________(DSL), but this requires special equipment at user locations.

5. Commercial television is broadcast over _______________ (VHF) and _________ (UHF) radio waves and can be received by any television set within range of the transmitter.

C. LANGUAGE FOCUS: ACRONYMS AND ABBREVIATIONS

The purpose of the following exercises is to develop language awareness in terms of acronyms and abbreviations.

C.1. In the technical register you will frequently encounter multi-word terms that are not pronounced in their complete form, their acronyms or abbreviations are used instead. Find at least five such terms and their acronyms in the text.

C.2. Read the following acronyms and abbreviations and decide on the correct way to pronounce them (as a new word/reading the letters separately) and identify the complete term.

List 1.

UHF

VHF

GPS

GLONASS

CD

ISDN

PC

DSL

E-mail

mi

C.3. What are the corresponding Romanian acronyms and abbreviations.

C.4. Think of other 10 abbreviations or acronyms that you are familiar with.

D. TRANSLATION

The purpose of this exercise is to develop translating skills.

D.1. Translate the following text into Romanian.

Personal radio communication is generally limited to short distances (usually a few kilometers), but powerful transmitters can send broadcast radio signals hundreds of kilometers. Shortwave radio, popular with amateur radio enthusiasts, uses a range of radio frequencies that are able to bounce off the ionosphere. This electrically charged layer of the atmosphere reflects certain frequencies of radio waves, such as shortwave frequencies, while allowing higher-frequency waves, such as microwaves, to pass through it. Amateur radio operators use the ionosphere to bounce their radio signals to other radio operators thousands of kilometers away.

E. SPEAKING

The purpose of these exercises is to develop speaking skills with a focus on presenting different applications of data transmission and computer networks.

E.1. Which are, in your opinion, the most important applications of GPS and GLONASS . Justify your answer.