- •U n I t 1 telecommunications
- •1 Read and memorize the following words and word-combinations:
- •2 Translate the following word-combinations into English:
- •Telecommunication
- •1 Find in the text English equivalents to the following Russian words and word combinations:
- •6 Fill the blanks using the words below:
- •Telephone
- •1 Using the text give derivatives from the following words and translate them into Russian:
- •2 Fill the blanks using the words below:
- •3 Answer the following questions:
- •4 Translate the following sentences from English into Russian:
- •5 Read the text, describe the principal of telephone communication
- •Radio communications
- •1 Answer the following questions:
- •3 Choose from part II the appropriate continuation of the sentences.
- •4 Translate without using a dictionary.
- •5 Look at the following short descriptions of processes:
- •1 Using the information from the first three texts translate the following one from Russian into English.
- •U n I t 2 modulation
- •1 Read and memorize the following words and word-combinations:
- •2 Translate the following word-combinations into English:
- •Modulation
- •1 Answer the following questions:
- •2 Reply to the following sentences with a suitable question:
- •3 Translate the following fragment into English using the information from the text.
- •4 Make up a summary of the text using the cliché:
- •Digital and analog modulation methods
- •1 What do the following abbreviations stand for?
- •2 Translate the following sentences into English:
- •3 Choose from part II the appropriate continuation of the sentences.
- •4 Read the following paragraph. Fill in each blank with a suitable word given below.
- •5 Translate without using a dictionary
- •6 Make a brief summary of the text.
- •Modulator and demodulator
- •1 Translate the following word-combinations into Russian:
- •2 Answer the following questions:
- •3 Read the following paragraph. Fill in each blank with a suitable word given below.
- •4 Translate without using a dictionary.
- •1 Using the information from the first three texts translate the following one from Russian into English.
- •Модуляция и помехоустойчивое кодирование
- •U n I t 3
- •1 Read and memorize the following words and word-combinations:
- •2 Translate the following word-combinations into English:
- •Transmission systems
- •1 Answer the following questions:
- •2 Complete the following simple process description of the function of a terminal repeater station:
- •3 Complete the following tree diagram:
- •4 Read the following paragraph. Fill in each blank with a suitable word given below.
- •Why optical fibers are useful and how they work
- •1 Below are the advantages of optical fibers. Match them with an appropriate explanation:
- •2 Discuss the importance of the above advantages in using optical fiber in public telephone networks. Try to rank the above advantages in order of importance.
- •3 Complete the following tables:
- •4 Read the following paragraph. Fill in each blank with a suitable word given below.
- •5 Reply to the following sentences with a suitable question:
- •6 Make a brief summary of the text.
- •1 Answer the following questions:
- •2 Read the following paragraph. Fill in each blank with a suitable word given below.
- •3 Translate the following sentences into English:
- •1 Using the information from the first three texts translate the following one from Russian into English.
- •Оптоволокно
- •U n I t 4
- •1 Read and memorize the following words and word-combinations:
- •2 Translate the following word-combinations into English:
- •Telephone exchanges
- •1 Answer the following questions:
- •2 Complete the following table: Main characteristics of the systems
- •3 Choose from part II the appropriate continuation of the sentences.
- •4 Put the verb in brackets into the correct tense.
- •5 Read the following paragraph. Fill in each blank with a suitable word given below.
- •6 Make up a summary of the text using the cliché:
- •Switching technologies
- •1 Integrated Digital Transmission and Switching
- •1 Complete the following table:
- •3 What are the advantages of using (large-scale) integrated circuits in an exchange?
- •4 Match the following terms with a suitable explanation:
- •5 Translate the following sentences into Russian:
- •Public Data Networks
- •1 Answer the following questions:
- •2 Match the facilities with the appropriate description:
- •3 Discuss in what situations and for which user groups the above facilities would be useful.
- •1 Using the information from the first three texts translate the following one from English into Russian.
- •Digital switches
- •Оглавление
- •Английский язык
- •246653, Г. Гомель, ул. Кирова, 34.
- •Английский язык
- •246653, Г. Гомель, ул. Кирова, 34.
1 Answer the following questions:
1 What is modulation in telecommunications?
2 What are the main kinds of modulation?
3 What is modem used for?
4 What is the aim of analogue modulation?
5 What is the aim of digital modulation?
6 What is line coding?
7 What kind of signals does a telephone line transfer?
8 How can computers communicate over a telephone line?
9 What is the aim of pulse modulation?
10 What technique allows transmitting several low pass information signals simultaneously over a common transmission medium?
2 Reply to the following sentences with a suitable question:
1 A high frequency sinusoid waveform is used as carrier signal.
2 To obtain the modulated signal parameters of a sine wave must be modified.
3 Modem is a short term for modulator-demodulator.
4 Each tone represents a message consisting of two digital bits.
5 Coaxial cables are used for FDM systems transmitting up to 10800 telephone channels.
6 A binary code is a coding system using binary digits 0 and 1.
3 Translate the following fragment into English using the information from the text.
Модуляция – процесс изменения одного или нескольких параметров высокочастотного модулируемого колебания под воздействием относительно низкочастотного управляющего модулирующего сигнала. В результате спектр управляющего сигнала переносится в область высоких частот, где передача электромагнитных сигналов посредством излучения более эффективна. Передаваемая информация заложена в управляющем сигнале. Роль переносчика информации выполняет высокочастотное колебание, называемое несущим. В качестве несущего могут быть использованы колебания различной формы (прямоугольные, треугольные и т. д.), однако чаще всего применяются гармонические колебания. В зависимости от того, какой из параметров несущего колебания изменяется, различают вид модуляции (амплитудная, частотная, фазовая и др.). Модуляция дискретным сигналом называется цифровой модуляцией или манипуляцией.
4 Make up a summary of the text using the cliché:
1 This text is about…
2 The title of the text is…
3 The text consists of three (four) parts…
4 At the beginning the author describes…
5 The main idea of the text is…
6 The text provides useful information on…
Text 2
Digital and analog modulation methods
In analog modulation, the modulation is applied continuously in response to the analog information signal.
Common analog modulation techniques are:
1 Amplitude modulation: double-sideband modulation DSB, double-sideband modulation with unsuppressed carrier (DSB-WC) (used on the radio AM band), double-sideband suppressed-carrier transmission (DSB-SC), double-sideband reduced carrier transmission (DSB-RC), single-sideband modulation, single-sideband modulation (SSB, or SSB-AM), very similar to single-sideband suppressed carrier modulation (SSB-SC), vestigial sideband modulation (VSB, or VSB-AM), quadrature amplitude modulation (QAM);
2 Angle modulation: frequency modulation (FM), phase modulation (PM)
In digital modulation, an analog carrier signal is modulated by a digital bit stream of either equal length signals or varying length signals. This can be described as a form of analog-to-digital conversion. The changes in the carrier signal are chosen from a finite number of alternative symbols (the modulation alphabet). In practical systems, these symbols are always chosen to be "orthogonal" to each other, resulting in a M-ary orthogonal modulation.
The most common digital modulation techniques are:
1 Phase-shift keying (PSK);
2 Frequency-shift keying (FSK);
3 Amplitude-shift keying (ASK) and its most common form, on-off keying (OOK);
4 Quadrature amplitude modulation (QAM) a combination of PSK and ASK;
5 Polar modulation like QAM a combination of PSK and ASK;
6 Continuous phase modulation (CPM)
7 Orthogonal frequency division multiplexing (OFDM) modulation, also known as discrete multitone (DMT);
8 Wavelet modulation;
9 Trellis coded modulation (TCM) also known as trellis modulation.
Of the two kinds of RF power amplifier, switching amplifiers cost less and use less battery power than linear amplifiers of the same output power. However, they only work with relatively constant-amplitude-modulation signals such as FM and some types of PM and polar modulation. Nevertheless, even though switching amplifiers are completely unsuitable for normal QAM constellations, often QAM modulators are used to drive switching amplifiers with these FM and other waveforms, and sometimes QAM demodulators are used to receive the signals put out by these switching amplifiers.
EXERCISES