Vocabulary

4.2 Complete the vocabulary (term) log, i.e. find out definition, part of speech, translation, synonyms and antonyms if possible, decode abbreviations.

Grammar

4.3 Choose the most suitable word or phrase in each sentence.

1) I will finish the letter now and you can post it ______ (after/later). 2) I have not seen Jim _______ (before/since) we worked together in London. 3) What were you doing ___________ (last evening/yesterday evening) when I called? 4) Did you live here _______ (in/since) 2008? 5) Diana has not finished her course ________ (already/yet). 6) What do you usually do ___________ (in the afternoon/this afternoon). 7) Have you seen Jean and Chris _____________ (nowadays/recently)? 8) Helen arrived here _____________ (at Thursday night/on Thursday night). 9) It’s really ages _________(since/when) I saw you last. 10) Ann is going to be famous _________ (once/one day).

Comprehension Check

4.4 Make up no less than 10 questions.

4.5 Read the following text and write a summary to it (no less than 7 sentences) in Russian and English.

Text 2 Transmission and Reception of Radio Waves

For the propagation and interception of radio waves, a transmitter and receiver are employed. A radio wave acts as a carrier of information-bearing signals; the information may be encoded directly on the wave by periodically interrupting its transmission (as in dot-and-dash telegraphy) or impressed on it by a process called modulation. The actual information in a modulated signal is contained in its sidebands, or frequencies added to the carrier wave, rather than in the carrier wave itself. The two most common types of modulation used in radio are amplitude modulation (AM) and frequency modulation (FM). Frequency modulation minimizes noise and provides greater fidelity than amplitude modulation, which is the older method of broadcasting. Both AM and FM are analog transmission systems, that is, they process sounds into continuously varying patterns of electrical signals, which resemble sound waves. Digital radio uses a transmission system in which the signals propagate as discrete voltage pulses, that is, as patterns of numbers; before transmission, an analog audio signal is converted into a digital signal, which may be transmitted in the AM or FM frequency range. A digital radio broadcast offers compact-disc-quality reception and reproduction on the FM band and FM-quality reception and reproduction on the AM band.

In its most common form, radio is used for the transmission of sounds (voice and music) and pictures (television). The sounds and images are converted into electrical signals by a microphone (sounds) or video camera (images), amplified, and used to modulate a carrier wave that has been generated by an oscillator circuit in a transmitter. The modulated carrier is also amplified, then applied to an antenna that converts the electrical signals to electromagnetic waves for radiation into space. Such waves radiate at the speed of light and are transmitted not only by line of sight but also by deflection from the ionosphere.

Receiving antennas intercept part of this radiation, change it back to the form of electrical signals, and feed it to a receiver. The most efficient and most common circuit for radio-frequency selection and amplification used in radio receivers is the superheterodyne. In that system, incoming signals are mixed with a signal from a local oscillator to produce intermediate frequencies (IF) that are equal to the arithmetical sum and difference of the incoming and local frequencies. One of those frequencies is applied to an amplifier. Because the IF amplifier operates at a single frequency, namely the intermediate frequency, it can be built for optimum selectivity and gain. The tuning control on a radio receiver adjusts the local oscillator frequency. If the incoming signals are above the threshold of sensitivity of the receiver and if the receiver is tuned to the frequency of the signal, it will amplify the signal and feed it to circuits that demodulate it, i.e., separate the signal wave itself from the carrier wave.

There are certain differences between AM and FM receivers. In an AM transmission the carrier wave is constant in frequency and varies in amplitude (strength) according to the sounds present at the microphone; in FM the carrier is constant in amplitude and varies in frequency. Because the noise that affects radio signals is partly, but not completely, manifested in amplitude variations, wideband FM receivers are inherently less sensitive to noise. In an FM receiver, the limiter and discriminator stages are circuits that respond solely to changes in frequency. The other stages of the FM receiver are similar to those of the AM receiver but require more care in design and assembly to make full use of FM's advantages. FM is also used in television sound systems. In both radio and television receivers, once the basic signals have been separated from the carrier wave they are fed to a loudspeaker or a display device (usually a cathode-ray tube), where they are converted into sound and visual images, respectively.

Unit 5 Cellular communication

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

Text 1 Cellular network

A cellular network or mobile network is a wireless network distributed over land areas called cells, each served by at least one fixed-location transceiver, known as a cell site or base station. In a cellular network, each cell uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed bandwidth within each cell.

When joined together these cells provide radio coverage over a wide geographic area. This enables a large number of portable transceivers (e.g., mobile phones, etc.) to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more than one cell during transmission.

Cellular networks offer a number of desirable features:

1) More capacity than a single large transmitter, since the same frequency can be used for multiple links as long as they are in different cells.

2) Mobile devices use less power than with a single transmitter or satellite since the cell towers are closer.

3) Larger coverage area than a single terrestrial transmitter, since additional cell towers can be added indefinitely and are not limited by the horizon.

Major telecommunications providers have deployed voice and data cellular networks over most of the inhabited land area of the Earth. This allows mobile phones and mobile computing devices to be connected to the public switched telephone network and public Internet. Private cellular networks can be used for research or for large organizations and fleets, such as dispatch for local public safety agencies or a taxicab company.

In a cellular radio system, a land area to be supplied with radio service is divided into regular shaped cells, which can be hexagonal, square, circular or some other regular shapes, although hexagonal cells are conventional. Each of these cells is assigned with multiple frequencies (f₁–f₆) which have corresponding radio base stations. The group of frequencies can be reused in other cells, provided that the same frequencies are not reused in adjacent neighboring cells as that would cause co-channel interference.

The increased capacity in a cellular network, compared with a network with a single transmitter, comes from the mobile communication switching system developed by Amos Joel of Bell Labs. That permitted multiple callers in the same area to use the same frequency by switching calls made using the same frequency to the nearest available cellular tower having that frequency available and from the fact that the same radio frequency can be reused in a different area for a completely different transmission. If there is a single plain transmitter, only one transmission can be used on any given frequency. Unfortunately, there is inevitably some level of interference from the signal from the other cells, which use the same frequency. This means that, in a standard FDMA system, there must be at least a one-cell gap between cells, which reuse the same frequency.

In the simple case of the taxi company, each radio had a manually operated channel selector knob to tune to different frequencies. As the drivers moved around, they would change from channel to channel. The drivers knew which frequency covered approximately what area. When they did not receive a signal from the transmitter, they would try other channels until they found one that worked. The taxi drivers would only speak one at a time, when invited by the base station operator (this is, in a sense, time division multiple access (TDMA)).

To distinguish signals from several different transmitters, frequency division multiple access (FDMA) and code division multiple access (CDMA) were developed.

With FDMA, the transmitting and receiving frequencies used in each cell are different from the frequencies used in each neighboring cell. In a simple taxi system, the taxi driver manually tuned to a frequency of a chosen cell to obtain a strong signal and to avoid interference from signals from other cells.

The principle of CDMA is more complex, but achieves the same result; the distributed transceivers can select one cell and listen to it.

Other available methods of multiplexing such as polarization division multiple access (PDMA) and time division multiple access (TDMA) cannot be used to separate signals from one cell to the next since the effects of both vary with position and this would make signal separation practically impossible. Time division multiple access, however, is used in combination with either FDMA or CDMA in a number of systems to give multiple channels within the coverage area of a single cell.

The most common example of a cellular network is a mobile phone (cell phone) network. A mobile phone is a portable telephone which receives or makes calls through a cell site (base station), or transmitting tower. Radio waves are used to transfer signals to and from the cell phone.

Modern mobile phone networks use cells because radio frequencies are a limited, shared resource. Cell-sites and handsets change frequency under computer control and use low power transmitters so that the usually limited number of radio frequencies can be simultaneously used by many callers with less interference.

A cellular network is used by the mobile phone operator to achieve both coverage and capacity for their subscribers. Large geographic areas are split into smaller cells to avoid line-of-sight signal loss and to support a large number of active phones in that area. All of the cell sites are connected to telephone exchanges (or switches), which in turn connect to the public telephone network.

In cities, each cell site may have a range of up to approximately ¹⁄₂ mile (0.80 km), while in rural areas, the range could be as much as 5 miles (8.0 km). It is possible that in clear open areas, a user may receive signals from a cell site 25 miles (40 km) away.

Since almost all mobile phones use cellular technology, including GSM, CDMA, and AMPS (analog), the term "cell phone" is in some regions, notably the US, used interchangeably with "mobile phone". However, satellite phones are mobile phones that do not communicate directly with a ground-based cellular tower, but may do so indirectly by way of a satellite.

5.2 Complete the vocabulary (term) log, i.e. find out definition, part of speech, translation, synonyms and antonyms if possible, decode abbreviations.

Grammar

5.3 Rewrite each question in indirect speech.

1) “What time does the film start, Peter?” I asked ______________________.

2) “Do you watch television every evening, Chris?” The interviewer asked _______________________.

3) “Why did you apply for the job?” asked the sales manager. The sales manager asked __________________________________.

4) “Are you taking much money with you to France?” My bank manager wanted to know _________________________________.

5) “When will I know the results of the examination?” Maria asked the examiner ______________________________________ .

6) “Are you enjoying your flight?” The flight attendant asked me __________.

7) “How does the photocopier work?” I asked the salesman _______________.

8) “Have you ever been to Japan, Paul?” Sue asked Paul ________________.

Comprehension Check

5.4 Make up no less than 10 questions.

5.5 Read the following text and write a summary to it (no less than 7 sentences) in Russian and English.

Text 2 Radio propagation

Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering.

Radio propagation is affected by the daily changes of water vapor in the troposphere and ionization in the upper atmosphere, due to the Sun. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.

Radio propagation is also affected by several other factors determined by its path from point to point. This path can be a direct line of sight path or an over-the-horizon path aided by refraction in the ionosphere, which is a region between approximately 60 and 600 km. Factors influencing ionospheric radio signal propagation can include sporadic-E, spread-F, solar flares, geomagnetic storms, ionospheric layer tilts, and solar proton events.

Radio waves at different frequencies propagate in different ways. At extremely low frequencies (ELF) and very low frequencies, the wavelength is much larger than the separation between the earth's surface and the D layer of the ionosphere, so electromagnetic waves may propagate in this region as a waveguide. Indeed, for frequencies below 20 kHz, the wave propagates as a single waveguide mode with a horizontal magnetic field and vertical electric field. The interaction of radio waves with the ionized regions of the atmosphere makes radio propagation more complex to predict and analyze than in free space. Ionospheric radio propagation has a strong connection to space weather. A sudden ionospheric disturbance or shortwave fadeout is observed when the x-rays associated with a solar flare ionize the ionospheric D-region. Enhanced ionization in that region increases the absorption of radio signals passing through it. During the strongest solar x-ray flares, complete absorption of virtually all ionospherically propagated radio signals in the sunlit hemisphere can occur. These solar flares can disrupt HF radio propagation and affect GPS accuracy

Since radio propagation is not fully predictable, such services as emergency locator transmitters, in-flight communication with ocean-crossing aircraft, and some television broadcasting have been moved to communications satellites. A satellite link, though expensive, can offer highly predictable and stable line of sight coverage of a given area.

Long distance propagation of radio waves depends on an invisible layer of charged particles, which envelops the Earth. This layer of charged particles known as the ionosphere has been in existence for millions of years. For those, who pioneered the long distance radio communication during the early part of the twentieth century, the ionosphere came as a boon. During the formative days of radio communication, radio scientists could not come to a definite conclusion about how radio waves propagated round the world. Both Radio and Television utilize radio wave, a form of electromagnetic wave that travels at a velocity of 3, 00000 km per second in vacuum. Its velocity gets changed very negligibly in a different medium, which is insignificant, because the earth is a very small place with a radius of only 6000-km. Communication between any two points on the earth is thus almost instantaneous. But electromagnetic waves travel in straight lines until they are deflected by something. The father of radio, Gug1ielmo Marconi himself was at a loss to explain how, on 12-th December, 1901, he established the first real long distance wireless communication between St. Johns, New Foundland, USA and Poldhu in the Southern Tip of England, a distance of more than 3,000 km across the Atlantic ocean. At that time, it was known that except for very short distances, the radio waves did not follow the natural curvature of the earth. Earth's curvature is a direct block to line-of-sight communication. When enough distance separates the two radio stations so that their antennas fall behind the curvature, the Earth itself blocks the transmitted signals from the receiver.

VHF

The radio frequencies above 30 MHz has the tendency to penetrate the ionosphere making them unsuitable for long distance propagation. So, the range of frequencies from 30 to 300 MHz (also 300 MHz and above), which are placed under the Very High Frequency (VHF) category are mainly used for line-of-sight communication. The most common example of line-of-sight communication is the TV Telecast. A TV transmission tower is made as tall as possible so that its signals can have a wide area of coverage. To receive a TV telecast, we have to turn our TV antenna (known as a Yagi antenna) towards the TV transmission tower. In areas where the TV transmission tower is located at a far away place from a viewer, the viewer has to increase the height of his TV receiving antenna. This means that both the transmitting and receiving antenna should literally see each other to make the communication effective. Otherwise, there should be some means to redirect the signal back to the receiver. Artificial Satellites in space (which houses active electronic relaying device), terrestrial relay station and passive reflectors (the metallic plates we see above the hills) are employed to extend the VHF coverage. Line-of-sight communication is considered reliable within a short distance.

To receive radio signals in the VHF ranges at a far away place from their place of origin, we need some kind of a reflector in between. You might have noticed big metallic plates on the mountain tops (or on top of other tall structures, which have a similarity to the roadside signboards. These are passive reflectors, which reflect VHF and UHF signals to far away places. A passive reflector is an object, which is not equipped with any kind of electronic circuitry to relay the radio signal.

Unit 6 Antennas

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

Text 1 Radio antennas

Antennas are required by any radio receiver or transmitter to couple its electrical connection to the electromagnetic field. Radio waves are electromagnetic waves, which carry signals through the air (or through space) at the speed of light with almost no transmission loss. Radio transmitters and receivers are used to convey signals (information) in systems including broadcast (audio) radio, television, mobile telephones, Wi-Fi (WLAN) data networks, trunk lines and point-to-point communications links (telephone, data networks), satellite links, many remote controlled devices such as garage door openers, and wireless remote sensors, among many others. Radio waves are also used directly for measurements in technologies including radar, GPS, and radio astronomy. In every case, the transmitters and receivers involved require antennas, although these are sometimes hidden (such as an antenna inside an AM radio or inside a laptop computer equipped with Wi-Fi).

Whip antenna on a car is a common example of an omnidirectional antenna. According to their applications and an available technology, antennas generally fall in one of two categories:

1. Omnidirectional or only weakly directional antennas, which receive or radiate more or less in all directions. These are employed when the relative position of the other station is unknown or arbitrary. They are also used at lower frequencies where a directional antenna would be too large, or simply to cut costs in applications where a directional antenna is not required.

2. Directional or beam antennas which are intended to preferentially radiate or receive in a particular direction or directional pattern.

In common usage "omnidirectional" usually refers to all horizontal directions, typically with reduced performance in the direction of the sky or the ground (a truly isotropic radiator is not even possible). A "directional" antenna usually is intended to maximize its coupling to the electromagnetic field in the direction of the other station, or sometimes to cover a particular sector such as a 120° horizontal fan pattern in the case of a panel antenna at a cell site.

One example of omnidirectional antennas is the very common vertical antenna or whip antenna consisting of a metal rod (often, but not always, a quarter of a wavelength long). A dipole antenna is similar but consists of two such conductors extending in opposite directions, with a total length that is often, but not always, a half of a wavelength long. Dipoles are typically oriented horizontally in which case they are weakly directional: signals are reasonably well radiated toward or received from all directions with the exception of the direction along the conductor itself; this region is called the antenna blind cone or null.

Both the vertical and dipole antennas are simple in construction and relatively inexpensive. The dipole antenna, which is the basis for most antenna designs, is a balanced component, with equal but opposite voltages and currents applied at its two terminals through a balanced transmission line (or to a coaxial transmission line through a so-called balun). The vertical antenna, on the other hand, is a monopole antenna. It is typically connected to the inner conductor of a coaxial transmission line (or a matching network); the shield of the transmission line is connected to ground. In this way, the ground (or any large conductive surface) plays the role of the second conductor of a dipole, thereby forming a complete circuit. Since monopole antennas rely on a conductive ground, a so-called grounding structure may be employed to provide a better ground contact to the earth or which itself acts as a ground plane to perform that function regardless of (or in absence of) an actual contact with the earth.

Antennas more complex than the dipole or vertical designs are usually intended to increase the directivity and consequently the gain of the antenna. This can be accomplished in many different ways leading to a plethora of antenna designs. The vast majority of designs are fed with a balanced line (unlike a monopole antenna) and are based on the dipole antenna with additional components (or elements) which increase its directionality. Antenna "gain" in this instance describes the concentration of radiated power into a particular solid angle of space, as opposed to the spherically uniform radiation of the ideal radiator. The increased power in the desired direction is at the expense of that in the undesired directions. Power is conserved, and there is no net power increase over that delivered from the power source (the transmitter.)

For instance, a phased array consists of two or more simple antennas, which are connected together through an electrical network. This often involves a number of parallel dipole antennas with a certain spacing. Depending on the relative phase introduced by the network, the same combination of dipole antennas can operate as a "broadside array" (directional normal to a line connecting the elements) or as an "end-fire array" (directional along the line connecting the elements). Antenna arrays may employ any basic (omnidirectional or weakly directional) antenna type, such as dipole, loop or slot antennas. These elements are often identical.

6.2 Complete the vocabulary (term) log, i.e. find out definition, part of speech, translation, synonyms and antonyms if possible, decode abbreviations.

Grammar

6.3 Rewrite each sentence, beginning as shown. Do not change the meaning.

1) What time does the next boat leave? Do you think you could tell me _________________?

2) Where can I change some money? Can you tell me _________________?

3) Where is the toilet? Could you possibly tell me ____________________?

4) How much does this pullover cost? I’d like to know ________________.

5) How do I get to Victoria Station? Can you explain _________________?

6) Does this train go to Gatwick Airport? Could you tell me ____________?

7) Where do you come from? Would you mind telling me ______________?

8) What do you think of London? Do you think you could tell me________?

Comprehension Check

6.4 Make up no less than 10 questions.

6.5 Read the following text and write a summary to it (no less than 7 sentences) in Russian and English.

Text 2 Broadcasting industry

The broadcasting industry consists of radio and television stations and networks that create content or acquire the right to broadcast taped television and radio programs. Networks transmit their signals from broadcasting studios via satellite signals to local stations or cable distributors. Broadcast signals then travel over cable television lines, satellite distribution systems, or the airwaves from a station’s transmission tower to the antennas of televisions and radios. Anyone in the signal area with a radio or television can receive the programming. Most Americans receive their television broadcasts through cable and other pay television providers. Although cable television stations and networks are included in this statement, cable and other pay television distributors are classified in the telecommunications industry.

Radio and television stations and networks broadcast a variety of programs, such as national and local news, talk shows, music programs, movies, other entertainment, and advertisements. Stations produce some of these programs, most notably news programs, in their own studios; however, much of the programming is produced outside the broadcasting industry. Establishments that produce filmed or taped programming for radio and television stations and networks but do not broadcast the programming are in the motion picture industry. Many television networks own production companies that produce their many shows.

Cable and other program distributors compensate local television stations and cable networks for rebroadcast rights. For popular cable networks and local television stations, distributors pay a fee per subscriber and/or agree to broadcast a less popular channel owned by the same network. Revenue for radio and television stations and networks also comes from the sale of advertising time. The rates paid by advertisers depend on the size and characteristics (age, gender, and median income, among others) of a program’s audience. Educational and noncommercial stations generate revenue primarily from donations by individuals, foundations, government, and corporations. These stations generally are owned and managed by public broadcasting organizations, religious institutions, or school systems.

Changes in Federal Government regulation and communication technology have affected the broadcast industry. The Telecommunications Act of 1996 relaxed ownership restrictions, an action that has had a tremendous impact on the industry. Instead of owning only one radio station per market, companies can now purchase up to eight radio stations in a single large market. These changes have led to a large-scale consolidation of radio stations. In some areas, five FM and three AM radio stations are owned by the same company and share the same offices. The ownership of commercial radio stations is increasingly concentrated. In television, owners are permitted two stations in larger markets and are restricted in the total number of stations nationwide (in terms of percent of all viewers).

The U.S. Federal Communications Commission (FCC) is a proponent of digital television (DTV), a technology that uses digital signals to transmit television programs. Digital signals consist of pieces of simple electronic code that can carry more information than conventional analog signals. This code allows for the transmission of better quality sound and higher resolution pictures, often referred to as high-definition television (HDTV). FCC regulations require all stations to broadcast digital signals as well as conventional analog signals. The current goal of the FCC is to have all stations stop broadcasting analog signals by 2007. However, because of the number of viewers who do not yet own television sets that are compatible with DTV, full implementation of the change from analog to digital broadcasting may take longer. After the switch is complete, any viewers using an analog TV and over-the-air signals will need a converter box to change the signal from digital to analog. Most television stations are currently broadcasting digital signals in response to FCC regulations. Many digital cable systems and satellite television providers already broadcast all their channels digitally, with some channels in high definition.

The transition to HDTV broadcasting has also accelerated the conversion of other aspects of television and radio production from analog to digital. Many stations have replaced specialized hardware with less specialized computers equipped with software that performs the same functions. Stations may use digital cameras, edit with computers, and store video on computer servers. Many major network shows now use HDTV cameras and editing equipment.

The transition to digital broadcasting also is occurring in radio. Most stations already store music, edit clips, and broadcast their analog signals with digital equipment. Satellite radio services, which offer 100 channels of digital sound, operate on a subscription basis, like pay television services. To compete, some radio stations are embedding a digital signal into their analog signals. With a specially equipped radio, these digital services offer better quality sound and display some limited text, such as the title of the song and the artist.

Unit 7 Antenna parameters

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

Text 1 Antenna parameters

Antennas are characterized by a number of performance measures, which a user would be concerned in selecting or designing an antenna for a particular application. Chief among these relate to the directional characteristics (as depicted in the antenna's radiation pattern) and the resulting gain. Even in omnidirectional (or weakly directional) antennas, the gain can often be increased by concentrating more of its power in the horizontal directions, sacrificing power radiated toward the sky and ground. The antenna’s power gain (or simply "gain") also takes into account the antenna's efficiency, and is often the primary figure of merit.

Resonant antennas are expected to be used around a particular resonant frequency; an antenna must therefore be built or ordered to match the frequency range of the intended application. A particular antenna design will present a particular feed point impedance. While this may affect the choice of an antenna, an antenna's impedance can also be adapted to the desired impedance level of a system using a matching network while maintaining the other characteristics (except for a possible loss of efficiency).

Although these parameters can be measured in principle, such measurements are difficult and require very specialized equipment. Beyond tuning a transmitting antenna using an SWR meter, the typical user will depend on theoretical predictions based on the antenna design or on claims of a vendor.

An antenna transmits and receives radio waves with a particular polarization which can be reoriented by tilting the axis of the antenna in many (but not all) cases. The physical size of an antenna is often a practical issue, particularly at lower frequencies (longer wavelengths). Highly directional antennas need to be significantly larger than the wavelength. Resonant antennas usually use a linear conductor (or element), or pair of such elements, each of which is about a quarter of the wavelength in length (an odd multiple of quarter wavelengths will also be resonant). Antennas that are required to be small compared to the wavelength sacrifice efficiency and cannot be very directional. Fortunately, at higher frequencies (UHF, microwaves) trading off performance to obtain a smaller physical size is usually not required.

While there are broadband traveling wave antennas such as the Beverage, which do not work by resonance, the vast majority of antennas are based on the monopole or dipole antenna, which function as resonators. At a particular frequency, their resonant frequency, waves of current and voltage bouncing back and forth between their ends create standing waves, thus these antennas function best at frequencies near their resonant frequency. The half-wave dipole is probably the most widely used antenna element. At its resonant frequency, the wavelength (figured by dividing the speed of light by the resonant frequency) is slightly over twice the length of the half-wave dipole (thus the name). The quarter-wave monopole antenna consists of one arm of a half-wave dipole, with the other arm replaced by a connection to ground or an equivalent ground plane (or counterpoise).

A Yagi-Uda array consists of a number of resonant dipole elements, only one of which is directly connected to the transmission line. The quarter-wave elements of a dipole or vertical monopole imitate a series-resonant electrical element due to the standing wave present along the conductor. At the resonant frequency, the standing wave has a current peak and voltage node (minimum) at the feed-point, thus presenting a lower impedance than at other frequencies. What's more, the large current and small voltage are in phase at that point, resulting in a purely resistive impedance, whereas away from the design frequency the feed-point impedance both rises and becomes reactive. Contrary to an ideal (lossless) series-resonant circuit, a finite resistance remains (corresponding to the relatively small voltage at the feed-point) due to the antenna's radiation resistance (as well as any actual electrical losses).

A common misconception is that the ability of a resonant antenna to transmit (or receive) fails at frequencies far from the resonant frequency. The reason a dipole antenna needs to be used at the resonant frequency has to do with the impedance match between the antenna and the transmitter or receiver (and its transmission line). For instance, a dipole using a fairly thin conductor will have a purely resistive feed point impedance of about 63 ohms at its design frequency. Feeding that antenna with a current of 1 ampere will require 63 volts of RF, and the antenna will radiate 63 watts (ignoring losses) of radio frequency power. If that antenna is driven with 1 ampere at a frequency 20% higher, it will still radiate as efficiently but in order to do that about 200 volts would be required due to the change in the antenna's impedance which is now largely reactive (voltage out of phase with the current). A typical transmitter would not find that impedance acceptable and would deliver much less than 63 watts to it; the transmission line would be operating at a high (poor) standing wave ratio. But using an appropriate matching network, that large reactive impedance could be converted to a resistive impedance satisfying the transmitter and accepting the available power of the transmitter.

7.2 Complete the vocabulary (term) log, i.e. find out definition, part of speech, translation, synonyms and antonyms if possible, decode abbreviations.

Grammar

7.3 Put each verb in brackets into either the present perfect simple or the present perfect continuous

1) Someone (eat) ________________ all cakes. I’ll have to buy some more. 2) What (you buy) _____________your sister for her birthday?

3) My throat is really sore. I (sing) ______________ all evening.

4) Brenda (learn) _____________Russian, but she finds it difficult.

5) How many people (you invite) _____________ to your party?

6) Those two cats (sit) ___________ on that branch for the last hour.

7) It (rain) all day! Why can’t it stop?

8) Diana (wear) ____________ twelve different dresses in the past week.

9) I (do) _____________ everything you asked. What should I do now?

10) Graham and Pauline (try) ___________ to find a house for ages, but they can’t find one they can afford.

Comprehension Check

7.4 Make up no less than 10 questions.

7.5 Read the following text and write a summary to it (no less than 7 sentences) in Russian and English.

Text 2 Antenna bandwidth

Although a resonant antenna has a purely resistive feed-point impedance at a particular frequency, many (if not most) applications require using an antenna over a range of frequencies. An antenna's bandwidth specifies the range of frequencies over which its performance does not suffer due to a poor impedance match. Also in the case of a Yagi-Uda array, the use of the antenna very far away from its design frequency reduces the antenna's directivity, thus reducing the usable bandwidth regardless of impedance matching.

Except for the latter concern, the resonant frequency of a resonant antenna can always be altered by adjusting a suitable matching network. To do this efficiently one would require remotely adjusting a matching network at the site of the antenna, since simply adjusting, a matching network at the transmitter (or receiver) would leave the transmission line with a poor standing wave ratio.

Instead, it is often desired to have an antenna whose impedance does not vary so greatly over a certain bandwidth. It turns out that the amount of reactance seen at the terminals of a resonant antenna when the frequency is shifted, say, by 5%, depends very much on the diameter of the conductor used. A long thin wire used as a half-wave dipole (or quarter wave monopole) will have a reactance significantly greater than the resistive impedance it has at resonance, leading to a poor match and generally unacceptable performance. Making the element using a tube of a diameter perhaps 1/50 of its length, however, results in a reactance at this altered frequency which is not so great, and a much less serious mismatch which will only modestly damage the antenna's net performance. Thus, rather thick tubes are typically used for the solid elements of such antennas, including Yagi-Uda arrays.

Rather than just using a thick tube, there are similar techniques used to the same effect such as replacing thin wire elements with cages to simulate a thicker element. This widens the bandwidth of the resonance. On the other hand, amateur radio antennas need to operate over several bands, which are widely separated from each other. This can often be accomplished simply by connecting resonant elements for the different bands in parallel. Most of the transmitter's power will flow into the resonant element while the others present a high (reactive) impedance and draw little current from the same voltage. A popular solution uses so-called traps consisting of parallel resonant circuits which are strategically placed in breaks along each antenna element. When used at one particular frequency band the trap presents a very high impedance (parallel resonance) effectively truncating the element at that length, making it a proper resonant antenna. At a lower frequency the trap allows the full length of the element to be employed, albeit with a shifted resonant frequency due to the inclusion of the trap's net reactance at that lower frequency.

The bandwidth characteristics of a resonant antenna element can be characterized according to its Q, just as one uses to characterize the sharpness of an L-C resonant circuit. However, it is often assumed that there is an advantage in an antenna having a high Q. After all, Q is short for "quality factor" and a low Q typically signifies excessive loss (due to unwanted resistance) in a resonant L-C circuit. However, this understanding does not apply to resonant antennas where the resistance involved is the radiation resistance, a desired quantity which removes energy from the resonant element in order to radiate it (the purpose of an antenna, after all!). The Q is a measure of the ratio of reactance to resistance, so with a fixed radiation resistance (an element's radiation resistance is almost independent of its diameter) a greater reactance off-resonance corresponds to the poorer bandwidth of a very thin conductor. The Q of such a narrowband antenna can be as high as 15. On the other hand, a thick element presents less reactance at an off-resonant frequency, and consequently a Q as low as five. These two antennas will perform equivalently at the resonant frequency, but the second antenna will perform over a bandwidth three times as wide as the "hi-Q" antenna consisting of a thin conductor.

Unit 8 Digital electronics

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

Text 1 Digital electronics

Digital electronics or digital (electronic) circuits are electronics that handle digital signals - discrete bands of analog levels, rather than by continuous ranges (as used in analogue electronics). All levels within a band of values represent the same numeric value. Because of this discretization, relatively small changes to the analog signal levels due to manufacturing tolerance, signal attenuation or parasitic noise do not leave the discrete envelope, and as a result are ignored by signal state sensing circuitry.

In most cases the number of these states is two, and they are represented by two voltage bands: one near a reference value (typically termed as "ground" or zero volts), and the other a value near the supply voltage. These correspond to the "false" ("0") and "true" ("1") values of the Boolean domain, respectively, yielding binary code.

Digital techniques are useful because it is easier to get an electronic device to switch into one of a number of known states than to accurately reproduce a continuous range of values.

Digital electronic circuits are usually made from large assemblies of logic gates, simple electronic representations of Boolean logic functions.

An advantage of digital circuits when compared to analog circuits is that signals represented digitally can be transmitted without degradation due to noise. For example, a continuous audio signal transmitted as a sequence of 1s and 0s, can be reconstructed without error, provided the noise picked up in transmission is not enough to prevent identification of the 1s and 0s. An hour of music can be stored on a compact disc using about 6 billion binary digits.

In a digital system, a more precise representation of a signal can be obtained by using more binary digits to represent it. While this requires more digital circuits to process the signals, each digit is handled by the same kind of hardware, resulting in an easily scalable system. In an analog system, additional resolution requires fundamental improvements in the linearity and noise characteristics of each step of the signal chain.

Computer-controlled digital systems can be controlled by software, allowing new functions to be added without changing hardware. Often this can be done outside of the factory by updating the product's software. So, the product's design errors can be corrected after the product is in a customer's hands.

Information storage can be easier in digital systems than in analog ones. The noise-immunity of digital systems permits data to be stored and retrieved without degradation. In an analog system, noise from aging and wear degrade the information stored. In a digital system, as long as the total noise is below a certain level, the information can be recovered perfectly.

Even when more significant noise is present, the use of redundancy permits the recovery of the original data provided too many errors do not occur.

In some cases, digital circuits use more energy than analog circuits to accomplish the same tasks, thus producing more heat, which increases the complexity of the circuits such as the inclusion of heat sinks. In portable or battery-powered systems, this can limit use of digital systems.

For example, battery-powered cellular telephones often use a low-power analog front-end to amplify and tune in the radio signals from the base station. However, a base station has grid power and can use power-hungry, but very flexible software radios. Such base stations can be easily reprogrammed to process the signals used in new cellular standards.

Digital circuits are sometimes more expensive, especially in small quantities.

Most useful digital systems must translate from continuous analog signals to discrete digital signals. This causes quantization errors. Quantization error can be reduced if the system stores enough digital data to represent the signal to the desired degree of fidelity. The Nyquist-Shannon sampling theorem provides an important guideline as to how much digital data is needed to accurately portray a given analog signal.

In some systems, if a single piece of digital data is lost or misinterpreted, the meaning of large blocks of related data can completely change. Because of the cliff effect, it can be difficult for users to tell if a particular system is right on the edge of failure, or if it can tolerate much more noise before failing.

Digital fragility can be reduced by designing a digital system for robustness. For example, a parity bit or other error management method can be inserted into the signal path. These schemes help the system detect errors, and then either correct the errors, or at least ask for a new copy of the data. In a state-machine, the state transition logic can be designed to catch unused states and trigger a reset sequence or other error recovery routine.

Digital memory and transmission systems can use techniques such as error detection and correction to use additional data to correct any errors in transmission and storage.

On the other hand, some techniques used in digital systems make those systems more vulnerable to single-bit errors. These techniques are acceptable when the underlying bits are reliable enough that such errors are highly unlikely.

A single-bit error in audio data stored directly as linear pulse code modulation (such as on a CD-ROM) causes, at worst, a single click. Instead, many people use audio compression to save storage space and download time, even though a single-bit error may corrupt the entire song.

8.2 Complete the vocabulary (term) log, i.e. find out definition, part of speech, translation, synonyms and antonyms if possible, decode abbreviations.

Grammar

8.3 Rewrite each sentence as direct speech.

1) Graham told Ian he would see him the following day. Graham said, “____________”

2) Pauline told the children their swimming things were not there. “__________”: said Pauline.

3) David told me my letter had arrived the day before. “_____________”, said David.

4) Shirley told Larry she would see him that evening. “ ____________”, said Shirley.

5) Bill told Stephen he hadn’t been at home that morning. “ ___________”, said Bill.

6) Margaret told John to phone her on the following day. “______________”, said Margaret.

7) Tim told Ron he was leaving that afternoon. “________________”, said Tim.

8) Christine told Michael she had lost her lighter the night before. “_____________”, said Christine.

Comprehension Check

8.4 Make up no less than 10 questions.

8.5 Read the following text and write a summary to it (no less than 7 sentences) in Russian and English.

Text 2 Video telephony

Video telephony comprises the technologies for the reception and transmission of audio-video signals by users at different locations, for communication between people in real-time.

At the dawn of the technology, video telephony also included image phones, which would exchange still images between units every few seconds over conventional POTS-type telephone lines, essentially the same as slow scan TV systems.

Currently video telephony usage has made significant inroads in government, healthcare, education and the news media. It is particularly useful to the deaf and speech-impaired who can use the technology with sign language and also with a video relay service, and well as to those with mobility issues or those who are located in distant places and are in need of tele medical or tele-educational services. It is also used in commercial and corporate settings to facilitate meetings and conferences, typically between parties that already have established relationships. Like all long distance communications technologies (such as phone and internet), by reducing the need to travel to bring people together the technology also contributes to reductions in carbon emissions, thereby helping to reduce global warming.

Video telephony developed in parallel with conventional voice telephone systems from the mid-to-late 20th century. Very expensive videoconferencing systems rapidly evolved throughout the 1980s and 1990s from proprietary equipment, software and network requirements to standards-based technologies that were readily available to the general public at a reasonable cost. Only in the late 20th century with the advent of powerful video codecs combined with high-speed Internet broadband and ISDN service did video telephony become a practical technology for regular use.

With the rapid improvements and popularity of the Internet, video telephony has become widespread thru the deployment of video-enabled mobile phones, plus videoconferencing and computer webcams, which utilize Internet telephony. In the upper echelons of government, business and commerce, telepresence technology, an advanced form of videoconferencing, has helped reduce the need to travel.

The highest ever video call took place on May 19, 2013 when British adventurer Daniel Hughes used a smartphone with a BGAN satellite modem to make a video call to the BBC from the summit of Mount Everest, at 8,848 m above sea level.

Video telephony can be categorized by its functionality, that is to its intended purpose, and also by its method of transmissions.

Videophones were the earliest form of video telephony, dating back to initial tests in 1927 by AT&T. During the late 1930s, the post offices of several European governments established public videophone services for person-to-person communications utilizing dual cable circuit telephone transmission technology. In the present day standalone videophones and UMTS video-enabled mobile phones are usually used on a person-to-person basis.

Videoconferencing saw its earliest use with AT&T's Picture phone service in the early 1970s. Transmissions were analog over short distances, but converted to digital forms for longer calls, again using telephone transmission technology. Popular corporate videoconferencing systems in the present day have migrated almost exclusively to digital ISDN and IP transmission modes due to the need to convey the very large amounts of data generated by their cameras and microphones. These systems are often intended for use in conference mode that is by many people in several different locations, all of whom can be viewed by every participant at each location.

Telepresence systems are a newer, more advanced subset of videoconferencing systems, meant to allow higher degrees of video and audio fidelity. Such high-end systems are typically deployed in corporate settings.

Mobile collaboration systems are another recent development, combining the use of video, audio, and on-screen drawing capabilities using newest generation hand-held electronic devices broadcasting over secure networks, enabling multi-party conferencing in real-time, independent of location.

A more recent technology encompassing these functions is TV cams. TV cams enable people to make video “phone” calls using video calling services, like Skype on their TV, without using a PC connection. TV cams are specially designed video cameras that feed images in real time to another TV camera or other compatible computing devices like smartphones, tablets and computers.

Personal computer based web cameras are an often modest form of video telephony, usually used for point-to-point videophone calls.

Each of the systems has its own advantages and disadvantages, including video quality, capital cost, degrees of sophistication, transmission capacity requirements, and cost of use.

Unit 9 Radar

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

Text 1 What is radar?

We can see objects in the world around us because light (usually from the Sun) reflects off them into our eyes. If you want to walk at night, you can shine a torch in front to see where you are going. The light beam travels out from the torch, reflects off objects in front of you, and bounces back into your eyes. Your brain instantly computes what this means: it tells you how far away objects are and makes your body move so you don't trip over things.

Radar works in much the same way. The word "radar" stands for radio detection and ranging, that gives a big clue as to what it does, and how it works. Imagine an airplane flying at night through thick fog. The pilots cannot see where they are going, so they use the radar to help them.

An airplane's radar is a bit like a torch that uses radio waves instead of light. The plane transmits an intermittent radar beam (so it sends a signal only part of the time) and, for the rest of the time, "listens" out for any reflections of that beam from nearby objects. If reflections are detected, the plane knows something is nearby—and it can use the time taken for the reflections to arrive to figure out how far away it is. In other words, radar is a bit like the echolocation system that "blind" bats use to see and fly in the dark.

Whether it is mounted on a plane, a ship, or anything else, a radar set needs the same basic set of components: something to generate radio waves, something to send them out into space, something to receive them, and some means of displaying information so the radar operator can quickly understand it.

The radio waves used by radar are produced by a piece of equipment called a magnetron. Radio waves are similar to light waves: they travel at the same speed—but their waves are much longer and have much lower frequencies. Light waves have wavelengths of about 500 nanometers (500 billionths of a meter, which is about 100–200 times thinner than a human hair), whereas the radio waves used by radar typically range from about a few centimeters to a meter—the length of a finger to the length of your arm—or roughly a million times longer than light waves.

Both light and radio waves are part of the electromagnetic spectrum, which means they are made up of fluctuating patterns of electrical and magnetic energy zapping through the air. The waves a magnetron produces are actually microwaves, similar to the ones generated by a microwave oven. The difference is that the magnetron in a radar has to send the waves many miles, instead of just a few inches, so it is much larger and more powerful.

Once the radio waves have been generated, an antenna, working as a transmitter, hurls them into the air in front of it. The antenna is usually curved so it focuses the waves into a precise, narrow beam, but radar antennas also typically rotate so they can detect movements over a large area. The radio waves travel outward from the antenna at the speed of light (186,000 miles or 300,000 km per second) and keep going until they hit something. Then some of them bounce back toward the antenna in a beam of reflected radio waves also traveling at the speed of light. The speed of the waves is crucially important. If an enemy jet plane is approaching at over 3,000 km/h (2,000 mph), the radar beam needs to travel much faster than this to reach the plane, return to the transmitter, and trigger the alarm in time. That is no problem, because radio waves (and light) travel fast enough to go seven times around the world in a second! If an enemy plane is 160 km (100 miles) away, a radar beam can travel that distance and back in less than a thousandth of a second.

The antenna doubles up as a radar receiver as well as a transmitter. In fact, it alternates between the two jobs. Typically, it transmits radio waves for a few thousandths of a second, and then it listens for the reflections for anything up to several seconds before transmitting again. Any reflected radio waves picked up by the antenna are directed into a piece of electronic equipment that processes and displays them in a meaningful form on a television-like screen, watched all the time by a human operator. The receiving equipment filters out useless reflections from the ground, buildings, and so on, displaying only significant reflections on the screen itself. Using radar, an operator can see any nearby ships or planes, where they are, how quickly they are traveling, and where they are heading. Watching a radar screen is a bit like playing a video game—except that the spots on the screen represent real airplanes and ships and the slightest mistake could cost many people's lives.

There is one more important piece of equipment in the radar apparatus. It has called a duplexer and it makes the antenna swap back and forth between being a transmitter and a receiver. While the antenna is transmitting, it cannot receive—and vice-versa.

9.2 Complete the vocabulary (term) log, i.e. find out definition, part of speech, translation, synonyms and antonyms if possible, decode abbreviations.

Grammar

9.3 Rewrite each sentence as indirect speech, beginning as shown.

1) “You can’t park here.”

The police officer told Jack ________________________________.

2) “I’ll see you in the morning, Helen.”

Peter told Helen _________________________________________.

3) “I’m taking 5.30 train tomorrow evening.”

Janet said ______________________________________________.

4) “The trousers have to be ready this afternoon.

Paul told the dry-cleaners _________________________________.

5) “I left my umbrella here two days ago.”

Susan told them _________________________________________.

6) “The parcel ought to be here by the end of the week.”

Brian said ______________________________________________.

7) “I like this hotel very much”.

Diana told me ___________________________________________.

8) “I think it’s going to rain tonight”.

William said ____________________________________________.

Comprehension Check

9.4 Make up no less than 10 questions.

9.5 Read the following text and write a summary to it (no less than 7 sentences) in Russian and English.

Text 2 Uses of Radar

Radar is still most familiar as a military technology. Radar antennas mounted at airports or other ground stations can be used to detect approaching enemy airplanes or missiles, for example. The United States has a very elaborate Ballistic Missile Early Warning System (BMEWS) to detect incoming missiles, with three major radar detector stations in Clear in Alaska, Thule in Greenland, and Fylingdales Moor in England. However, it is not only the military men that use radar. Most civilian airplanes and larger boats and ships now have radar too as a general aid to navigation. Every major airport has a huge radar-scanning dish to help air traffic controllers guide planes in and out, whatever the weather. Next time you head for an airport, look out for the rotating radar dish mounted on or near the control tower.

You may have seen police officers using radar guns by the roadside to detect people who are driving too fast. These are based on a slightly different technology called Doppler radar. You have probably noticed that a fire engine's siren seems to drop in pitch as it screams past. As the engine drives toward you, the sound waves from its siren arrive more often because the speed of the vehicle makes them travel a bit faster. When the engine drives away from you, the vehicle's speed works the opposite way—making the sound waves travel slower and arrive less often. Therefore, you hear quite a noticeable drop in the siren's pitch at the exact moment when it passes by. This is called the Doppler effect.

The same science is at work in a radar speed gun. When a police officer fires a radar beam at your car, the metal bodywork reflects the beam straight back. Nevertheless, the faster your car is traveling, the more it will change the frequency of the radio waves in the beam. Sensitive electronic equipment in the radar gun uses this information to calculate how fast your car is going.

Radar has many scientific uses. Doppler radar is also used in weather forecasting to figure out how fast storms are moving and when they are likely to arrive in particular towns and cities. Effectively, the weather forecasters fire out radar beams into clouds and use the reflected beams to measure how quickly the rain is traveling and how fast it is falling. Scientists use a form of visible radar called LIDAR (light detection and ranging) to measure air pollution with lasers. Archeologists and geologists point radar down into the ground to study the composition of the Earth and find buried deposits of historical interest.

One place radar is not used is on board submarines. Electromagnetic waves do not travel readily through dense seawater (that is why it is dark in the deep ocean). Instead, submarines use a very similar system called SONAR (Sound Navigation And Ranging), which uses sound to "see" objects instead of radio waves.

Radar is extremely effective at spotting enemy aircraft and ships—so much so that military scientists had to develop some way around it! If you have a superb radar system, chances are your enemy has one too. If you can spot his airplanes, he can spot yours. Therefore, you really need airplanes that can somehow "hide" themselves inside the enemy's radar without being spotted. Stealth technology is designed to do just that. You may have seen the US air force's sinister-looking B2 stealth bomber. Its sharp, angular lines and metal-coated windows are designed to scatter or absorb beams of radio waves so enemy radar operators cannot detect them. A stealth airplane is so effective at doing this that it shows up on a radar screen with no more energy than a small bird!

Unit 10 Communication standards

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

Text 1 Communication protocol

In telecommunications, a communications protocol is a system of rules that allow two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. These are the rules or standard that defines the syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both.

Communicating systems use well-defined formats (protocol) for exchanging messages. Each message has an exact meaning intended to elicit a response from a range of possible responses pre-determined for that particular situation. The specified behavior is typically independent of how it is to be implemented. Communications protocols have to be agreed upon by the parties involved. To reach agreement, a protocol may be developed into a technical standard. A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: protocols are to communications as programming languages are to computations.

The information exchanged between devices—through a network, or other media—is governed by rules and conventions that can be set out in technical specifications called communications protocol standards. The nature of a communication, the actual data exchanged and any state-dependent behaviors, is defined by its specification.

In digital computing systems, the rules can be expressed by algorithms and data structures. Expressing the algorithms in a portable programming language makes the protocol software operating system independent.

Operating systems usually contain of a set of cooperating processes that manipulate shared data to communicate with each other. This communication is governed by well-understood protocols, which can be embedded in the process code itself.

In contrast, because there is no common memory, communicating systems have to communicate with each other using a shared transmission medium. Transmission is not necessarily reliable, and individual systems may use different hardware and/or operating systems.

To implement a networking protocol, the protocol software modules are interfaced with a framework implemented on the machine's operating system. This framework implements the networking functionality of the operating system. The best known frameworks are the TCP/IP model and the OSI model.

At the time the Internet was developed, layering had proven to be a successful design approach for both compiler and operating system design and, given the similarities between programming languages and communications protocols, layering was applied to the protocols as well. This gave rise to the concept of layered protocols, which nowadays forms the basis of protocol design.

Systems typically do not use a single protocol to handle a transmission. Instead, they use a set of cooperating protocols, sometimes called a protocol family or protocol suite. Some of the best-known protocol suites include IPX/SPX, X.25, AX.25, AppleTalk and TCP/IP.

The protocols can be arranged based on functionality in groups, for instance there is a group of transport protocols. The functionalities are mapped onto the layers, each layer solving a distinct class of problems relating to, for instance: application-, transport-, internet- and network interface-functions. To transmit a message, a protocol has to be selected from each layer, so some sort of multiplexing/demultiplexing takes place. The selection of the next protocol is accomplished by extending the message with a protocol selector for each layer.

Despite their numbers, networking protocols show little variety, because all networking protocols use the same underlying principles and concepts, in the same way. So, the use of a general purpose programming language would yield a large number of applications only differing in the details. A suitably defined (dedicated) protocolling language would therefore have little syntax, perhaps just enough to specify some parameters or optional modes of operation, because its virtual machine would have incorporated all possible principles and concepts making the virtual machine itself a universal protocol. The protocolling language would have some syntax and a lot of semantics describing this universal protocol and would therefore in effect be a protocol, hardly differing from this universal networking protocol. In this (networking) context a protocol is a language.

The notion of a universal networking protocol provides a rationale for standardization of networking protocols; assuming the existence of a universal networking protocol, development of protocol standards using a consensus model (the agreement of a group of experts) might be a viable way to coordinate protocol design efforts.

Networking protocols operate in very heterogeneous environments consisting of very different network technologies and a (possibly) very rich set of applications, so a single universal protocol would be very hard to design and implement correctly. Instead, the IETF decided to reduce complexity by assuming a relatively simple network architecture allowing decomposition of the single universal networking protocol into two generic protocols, TCP and IP, and two classes of specific protocols, one dealing with the low-level network details and one dealing with the high-level details of common network applications (remote login, file transfer, email and web browsing). ISO choose a similar but more general path, allowing other network architectures, to standardize protocols.

10.2 Complete the vocabulary (term) log, i.e. find out definition, part of speech, translation, synonyms and antonyms if possible, decode abbreviations.

Grammar

10.3 Put each verb in brackets into a suitable verb form.

1. Why didn’t you phone? If I (know) ___________________you were coming, I (meet) ____________________you at the airport.

2. It is a pity you missed the party. If you (come) ________________, you (meet) my friends from Hungary.

3. If we (have) _________________some tools, we (be able) _______________to repair the car, but we do not have any with us.

4. If you (not help) ________________me, I (not pass) _________________ the exam.

5. It’s a beautiful house, and I (buy)____________________it if I (have) _____________the money, but I can’t effort it.

6. I can’t imagine what I (do) __________________with the money if I (win) _________________the lottery.

7. If Marc (train) ______________harder, he (be) ________________a good runner.

8. If Claire (listen) _____________to her mother, she (not marry) ____________David in the first place.

Comprehension Check

10.4 Make up no less than 10 questions.

10.5 Read the following text and write a summary to it (no less than 7 sentences) in Russian and English.

Text 2 HD Radio

High Definition Technology- an overview or tutorial of the basics of the technology for HD Radio, High Definition Radio, the digital radio system developed by iBiquity and chosen as the digital radio system for broadcasting with the USA.

Digital technology is being applied to many areas of radio communication including radio broadcasting as it offers some significant advantages. While DAB digital radio is becoming established in some areas of the globe, the system that has been chosen for use in the USA is known as HD, or High Definition, Radio. Using HD Radio, will enable high quality audio to be received along with the ability to incorporate many new features and facilities.

The HD Radio system has been developed by iBiquity, and has now been selected by the FCC in the USA. It will take the place of both the existing AM and FM transmissions, and offers many advantages for both listeners and broadcasters alike:

1) Improved audio quality - it is claimed that HD Radio broadcasts on the AM bands will be as good as current FM services and those on the FM band will offer CD quality audio.

2) Reduced levels of interference. AM transmissions in particular are prone to static pops and bangs as well as high levels of background noise. HD Radio will almost eliminate this.

3. Opportunity to use additional data services. By using digital technology, HD Radio provides the opportunity to add data services such as scrolling program information, song titles, artist names, and much more.

4. There is also the possibility of adding more advanced services such as surround sound, multiple audio sources, on-demand audio services, etc.

5. Easy transition for broadcasters and listeners. Although new HD Radio receivers are required to receive the new transmissions in their digital format there is considerable re-use of infrastructure and spectrum.