Text 1. What the Internet is

The Internet is an International computer Network made up of thousands of networks linked together. All these computers communicate with one another; they share data, resources, transfer information, etc. To do it they need to use the same language or protocol: TCP / IP (Transmission Control Protocol / Internet Protocol) and every computer is given an address or IP number. This number is a way to identify the computer on the Internet.

Getting connected

To use the Internet you basically need a computer, the right connection software and a modem to connect your computer to a telephone line and then access your ISP (Internet Service Provider).

The modem (modulator-demodulator) converts the digital signals stored in the computer into analogue signals that can be transmitted over telephone lines. There are two basic types: external with a cable that is plugged into the computer via a USB port, and internal, an expansion card inside the computer. A PC card modem is a different, more versatile option for laptops and mobile phones.

At first most computers used a dial-up telephone connection that worked through the standard telephone line. Now a broadband connection, a high data transmission rate Internet connection, has become more popular: either ADSL (Asymmetric Digital Subscriber Line), which allows you to use the same telephone line for voice and fast access to the Internet, or cable, offered by most TV cable providers.

The basic equipment has changed drastically in the last few years. You no longer need a computer to use the Internet. Web TV provides email and access to the Web via a normal TV set plus a high-speed modem. More recently, 3 Generation mobile phones and PDAs, personal digital assistants, also allow you to go online with wireless connections, without cables.

Telephone lines are not essential either. Satellites orbiting the earth enable your computer to send and receive Internet files. Finally, the power-line Internet, still under development, provides access via a power plug.

Components of the Internet

The Internet consists of many systems that offer different facilities to users. WWW, the World Wide Web, is a collection of files or pages containing links to other documents on the Net. It's by far the most popular system. Most Internet services are now integrated on the Web.

Email, or electronic mail, for the exchange of messages and attached files. Mailing lists (or listservs) based on programs that send messages on a certain topic to all the computers whose users have subscribed to the list.

Chatand instant messaging, for real-rime conversations; you type your messages on the keyboard.

Internet telephone, a system that lets people make voice calls via the Internet.

Video conference, a system that allows the transmission of video and audio signals in real time so the participants can exchange data, talk and see one another on the screen.

File Transfer Protocol (FTP),used to transfer files between computers. Newsgroups, where people send, read and respond to public bulletin board messages stored on a central computer.

TELNET, a program that enables a computer to function as a terminal working from a remote computer and so use online databases or library catalogues.

Vocabulary

4.2 Compile the vocabulary (term) log as shown in the preface (part of speech, definition, translation, synonyms and antonyms if possible, example of use). Words (concepts) are given below:

Software, an expansion card, a dial-up telephone connection, a broadband connection, a power plug, a remote computer, power-line Internet, an attached file, to subscribe to, USB port, modem, laptop, digital assistant.

4.3 Find in the text and suggest English equivalents for the following:

Широкополосное соединение; внутренний; предлагать различные технические возможности; состоять из; существенный, важный; отвечать на электронные объявления, внешний.

Comprehension Check

4.4 Read the text and answer the following questions.

1) What is the Internet? 2) What happens when computers communicate with one another? 3) What is every computer given? 4) What do you need to use the Internet? 5) What does the modem convert? 6) What types of modems are there? 7) At first most computers used a dial-up telephone connection, didn’t they? 8) What has become more popular nowadays? 9) Does Web TV provide email and access to the Web via a normal TV set plus a high-speed modem? 10) Aren’t telephone lines essential either? 11) What are basic components of the Internet?

4.5 Read these sentences and decide if they are True or False. If they are false, correct them.

1) The Internet and the World Wide Web are synonyms.

2) Computers need to use the same protocol (TCP / IP) to communicate with each other.

3) Web TV can provide access to the Net.

4) ADSL and cable are two types of dial-up connections.

5) External, internal and PC card are types of connections.

6) Information can be sent through telephone lines, satellites and power lines.

7) The computer IP number is a way to identify it on the Internet.

4.6 Read the following text, guess or suggest a title to it, and write a summary (approximately 7 sentences).

Text 2.________________________

Communication signals sent over copper wire are primarily direct electrical current (DC) which is modulated to represent a frequency. Any other electrical current near the communication wire (including other communication signals) can introduce interference and noise. Multiple communication wires within a cable bundle can induce interfering electro-magnetic currents, or "cross-talk". This happens when one signal within the cable is so strong that it introduces a magnetic field into an adjacent wire, or communication pair. Energy sources such as power transmission lines or fluorescent lighting fixtures can cause electromagnetic interference. This interference can be minimized by twisting a pair of wires around a common axis, or by the use of metallic shielding, or both. The twisting effectively creates a magnetic shield that helps to minimize “crosstalk”.

Twisted pair is the ordinary copper wire that provides basic telephone services to the home and many businesses. In fact, it is referred to as "Plain Old Telephone Service" (POTS). The twisted pair is composed of two insulated copper wires twisted around one another. The twisting is done to prevent opposing electrical currents traveling along the individual wires from interfering with each other.

Each connection on twisted pair requires both wires. Since some telephone sets or desktop locations require multiple connections, twisted pair is sometimes installed in two or more pairs, all within a single cable. For some business locations, twisted pair is enclosed in a shield that functions as a ground. This is known as shielded twisted pair (STP). Ordinary wire to the home is unshielded twisted pair (UTP). Twisted pair is now frequently installed with two pairs to the home, with the extra pair making it possible to add another line - perhaps for modem use.

Twisted pair comes with each pair uniquely color coded when it is packaged in multiple pairs. Different uses such as analog, digital, and Ethernet require different pair multiples. There is an EIA/TIA standard for color coding of wires, wire pairs, and wire bundles. The color coding allows technicians to install system wiring in a standard manner. A basic single telephone line in a home will use the red and green wire. If a second phone line is provided, it will use the yellow and black wire. The most common cause of telecommunication system problems is incorrect wiring. This wiring protocol is for standard telephone set jack connections. Data systems use different arrangements and color codes. The most common is the EIA/TIA standard. Please note that NEMA and ICEA have color codes for electrical wire. Do not confuse these with telecommunication wire color coding standards.

Twisted pair is categorized by the number of twists per meter. A greater number of twists provides more protection against crosstalk, and other forms of interference and results in a better quality of transmission. For data transmission, better quality equates to fewer transmission errors. Later in this chapter, we'll look at the effects of transmission errors as they impact on throughput and delay times.

There are two types of twisted pair cables used for most in-building situations today - Category 3 UTP (CAT 3) and Category 5 UTP (CAT 5). However, as of the writing of this handbook, all new and replacement installations use CAT 5. These cables have been developed based on a set of standards issued by the EIA/TIA (Electronic Industry Association/Telecommunications Industry Association). CAT 3 is used primarily for telephone cabling and 10Base-T install at ions, while CAT 5 is used to support 10/100Base-T installations. CAT 5 wiring can also be used for telephone systems. Therefore, most new install at ions use CAT 5 instead of CAT 3. The CAT 5 cable is pulled to a cubicle or office and connected to a universal wall plate that allows for installation of data and voice communication systems. Category 5E (CAT 5E) has been developed to accommodate GigE installations. CAT 5E is manufactured and tested under stricter guidelines than CAT 3 or CAT 5. Two new standards - CAT 6 and CAT 7 - have been adopted to meet criteria for 106igE (and higher) transmission speeds.

4.7 Make up 10 questions of your own using the information in text 2.

Unit 5

5.1 Read and translate the text. Use a dictionary to help you.

Text 1.Multiplexing

A channel is the bridge between a source and a receiver. In the early days of electrical wire communications, each channel was used to transmit only a single signal. Proliferation of separate channels could not be permitted to continue as communications expanded.

In the majority of applications, a variety of signals must be transmitted on a single channel. The channel must, therefore, be shared among the various users. The process of sending multiple signals on a single channel is called multiplexing. If multiple signals are to be sent on a same channel, the various signals must not overlap; they must be separable. In a mathematical sense, the various signals must be orthogonal.

The form of multiplexing used in everyday speech requires time separation. In a conversation, the participants try not to speak at the same time. There are many other ways that signals can be nonoverlapping.

Frequency – division multiplexing (FDM) is the technique used to in standard analog transmit systems such as AM radio, FM radio, and television. It takes advantage of the observation that all frequencies of a particular message waveform can be easily shifted by a constant amount. The shifting is performed using a carrier signal. The original message is multiplied by a sinusoid.

The multiplexed signals can be separated using frequency gates (bandpass filters). The frequencies can then be shifted back to the baseband using demodulators.

Frequency - division multiplexing is sometimes used to create a composite baseband signal. For example, in FM stereo, the two audio signals are frequency multiplexed to produce a new baseband signal. One of the audio signals occupies the band of frequencies between DC and 15kHz, whereas the second audio signal is shifted by 38kHz. It then occupies a band between 23 and 53 kHz. There is a complete duality between the time and frequency domain.

An analog signal can be transmitted by first sampling the waveform. In accordance with the sampling theorem, the number of samples required each second is at least twice the highest frequency of the waveform. If each pulse occupies only a fraction of the time spacing between samples, the time axis can be shared with other sampled signals.

The three signals are said to be time – division multiplexed. If the pulses are made narrower, additional signals can be multiplexed. Of course, the narrower the pulses are, the wider the bandwidth is.

Vocabulary

5.2 Compile the vocabulary (term) log as shown in the preface (part of speech, definition, translation, synonyms and antonyms if possible, example of use). Words (concepts) are given below.

Multiplexing; frequency; proliferation; оrthogonal; time separation; frequency-division multiplexing; to overlap; a carrier signal; sampling; bandpass filter; bandwidth; a baseband signal; time axis.

5.3 Find in the text and/or suggest English equivalents for the following:

Электропроводная связь; многократный (множественный); сдвигать, перемещать; переключать; теорема о дискретном представлении (теорема Шеннона-Котельникова); использовать возможность.

Grammar

5.4 Read and translate the sentences containing complex subject:

1) The original shifted signal is modified to contain the carrier sinusoid. 2) The three signals are said to be time – division multiplexed. 3) Realizations of either N or T in a queuing system should be expected to fluctuate markedly about their means. 4) This phenomenon is said to be discovered in 1864. 5) He seems to know these results very well. 6) The laser beam seems to have almost unlimited possibilities. 7) The discovery of the theory of two random variables is sure to be of great value. 8) This quantizer is said to be uniform since all of the steps are of equal size.

Comprehension Check

5.5Answer the following questions.

1) What is a channel? 2) How were channels used in the early days of electrical wire communications? 3) What is called multiplexing? 4) In what case must the various signals be separated? 5) Where is frequency – division multiplexing used? 6) What is the original messagemultiplied by? 7) What do we use to separate the multiplexed signals? 8) What is there between time and frequency domain? 9) What happens if each pulse occupies only a fraction of the time spacing between samples? 10) In what cases can the bandwidth be wider?

5.6 Translate the following equivalents and memorize them.

In the early days of, separate channels, to be sent on a same channel, in a mathematical sense, at the same time, the original message, to create a composite baseband signal, to occupy the band of frequencies, in accordance with.

Developing Language Skills

5.7. Insert the following prepositions:to, with, over, of, on, into.

When terrestrial multipoint communication became popular, the general approach was to maximize the distance … which signals could be transmitted. The cellular radio concept is based… intentionally reducing the signal coverage area. Space-division multiplexing can also be accomplished… highly directional antennas. Some satellite systems divide the earth… regions and do simultaneous transmission… different signals… these regions using directional antennas.

5.8 Read the following text, guess or suggest a title to it, and write a summary (approximately 7 sentences).

Text 2. _________________

The 24 satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours. These satellites are travelling at speeds of roughly 7,000 miles an hour.

GPS satellites are powered by solar energy. They have backup batteries onboard to keep them running in the event of a solar eclipse, when there's no solar power. Small rocket boosters on each satellite keep them flying in the correct path.

Here are some other interesting facts about the GPS satellites (also called NAVSTAR, the official U.S. Department of Defense name for GPS):

The first GPS satellite was launched in 1978. A full constellation of 24 satellites was achieved in 1994. Each satellite is built to last about 10 years. Replacements are constantly being built and launched into orbit. A GPS satellite weighs approximately 2,000 pounds and is about 17 feet across with the solar panels extended. Transmitter power is only 50 watts or less.

What's the signal?GPS satellites transmit two low power radio signals, designated L1 and L2. Civilian GPS uses the L1 frequency of 1575.42 MHz in the UHF band. The signals travel by line of sight, meaning they will pass through clouds, glass and plastic but will not go through most solid objects such as buildings and mountains.

A GPS signal contains three different bits of information - a pseudorandom code, ephemeris data and almanac data. The pseudorandom code is simply an I.D. code that identifies which satellite is transmitting information. You can view this number on your Garmin GPS unit's satellite page, as it identifies which satellites it's receiving.

Ephemeris data, which is constantly transmitted by each satellite, contains important information about the status of the satellite (healthy or unhealthy), current date and time. This part of the signal is essential for determining a position.

The almanac data tells the GPS receiver where each GPS satellite should be at any time throughout the day. Each satellite transmits almanac data showing the orbital information for that satellite and for every other satellite in the system.

5.9 Make up 10 questions of your own using the information in text 2.

Unit 6

6.1 Read and translate the text. Use a dictionary to help you.