- •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.
2 Translate the following word-combinations into English:
Оптоволокно со ступенчатым профилем распределения показателей преломления, оптоволокно с градиентным показателем преломления, перекрытие импульсов, наложение сигналов, светоизлучающий диод, автоматическая телефонная станция, цифровая телефонная станция, двухпроводная воздушная линия связи, четырехпроводная линия связи, радиорелейная система, медный сердечник, непрозрачная оболочка оптического волокна, волоконно-оптическая связь, диапазон высоких частот, затухание сигнала.
Text 1
Transmission systems
Many different transmission systems are used in telecommunications technology. Transmission on open-wire lines was the earliest method used for telephone traffic, and this method is still used in the local networks of many countries. Nowadays, due to the demands on operating reliability, local networks are built up using aerial or underground cable.
Since 1965, satellites have become increasingly important for long distance communication, especially across the oceans. In principle, the satellite operates as an intermediate repeater; signals are received, amplified and transmitted to the ground station on the receive side. Satellites use the same frequency band as radio relay systems.
Radio relay links operate with line of sight between the send and receive stations. In principle, the greater the diameter of the parabola in relation to the wavelength, the higher the degree of directivity.
Between the subscriber and the local exchange two-wire circuits are used, often placed in symmetric cable pairs. Between the local and transit exchanges either two- or four-wire circuits are used. On longer routes, it may be advantageous to use PCM on coaxial cable. These cables are also used for FDM systems transmitting up to 10 800 telephone channels. At regular intervals along the coaxial line, line amplifiers are provided; these are mounted in underground housings and are called ‘intermediate repeaters’. In principle, the greater the number of channels transmitted, the larger the number of repeaters required.
In terminal repeater stations, situated in ground stations and transit exchanges, speech signals are modulated and combined before transmission. Each separate conversation is shifted to a significantly higher frequency range. This is done in a number of steps. First, by selecting suitable modulation frequencies, the conversations can be placed next to each other along the frequency axis. Then, they are transmitted as a group to the receive side where a similar station demodulates the signals and extracts the various conversations before they are transmitted in two- or four-wire circuits to another transit exchange.
EXERCISES
1 Answer the following questions:
1 Why are local networks built up using cable rather than open wire?
2 What type of cables is used for systems which transmit up to 10,800 telephone channels?
3 What is another term for ‘intermediate repeaters’?
4 What are the three functions of a satellite?
5 What is the directivity of a radio relay system proportional to?