Файл: Учебнометодическое пособие по английскому языку для специалистов и бакалавров 2 курса института ртс. Москва 2019.docx
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| МИНИСТЕРСТВО ОБРАЗОВАНИЯ И НАУКИ РОССИЙСКОЙ ФЕДЕРАЦИИ МИРЭА – РОССИЙСКИЙ ТЕХНОЛОГИЧЕСКИЙ УНИВЕРСИТЕТ  Т.В. КУДИНОВА, Н.А.МИРОЛЮБОВА, Н.В.ДИДЫК АНГЛИЙСКИЙ ЯЗЫК Учебно-методическое пособие по английскому языку для специалистов и бакалавров 2 курса института РТС. Москва – 2019 |
, кандидат культурологических наук, доцент, зав. Кафедрой лингвистики и межкультурной коммуникации Института славянской культуры РГУ им. Косыгина
Васильев Андрей Георгиевич, доктор физико-математических наук, профессор, директор института Радиотехнических и телекоммуникационных систем.
Table of contents
Unit 1 4
Text A 4
Text B 8
Text C 12
Text D 14
Text E 18
20
Unit 2 21
Text A 21
Text B 26
Text C 33
Text D 36
Unit 3 40
Text A 40
Text B 42
Text C 45
Unit 4 48
Text A 48
Text B 51
Text C 53
Text D 55
Text E 57
Text F 60
References 63
Сведения об авторах 65
Unit 1
Text A
TelecommunicationsTelecommunication is the transmission of signs, signals, messages, words, writings, images and sounds or information of any nature by wire, radio, optical or electromagnetic systems.Telecommunication occurs when the exchange of information between communication participants includes the use of technology. It is transmitted either electrically over physical media, such as cables, or via electromagnetic radiation. Such transmission paths are often divided into communication channels which afford the advantages of multiplexing. The Latin term communication is considered the social process of information exchange, the term telecommunications is often used in its plural form because it involves many different technologies.Key conceptsModern telecommunication is founded on a series of key concepts that experienced progressive development and refinement in a period of well over a century.Basic Telecommunication technologies may primarily be divided into wired and wireless methods. Overall though, a basic telecommunication system consists of three main parts that are always present in some form or another: • A transmitter that takes information and converts it to a signal.• A transmission medium, also called the physical channel that carries the signal. An example of this is the "free space channel".• A receiver that takes the signal from the channel and converts it back into usable information for the recipient.For example, in a radio broadcasting station the station's large power amplifier is the transmitter; and the broadcasting antenna is the interface between the power amplifier and the "free space channel". The free space channel is the transmission medium; and the receiver's antenna is the interface between the free space channel and the receiver. Next, the radio receiver is the destination of the radio signal, and this is where it is converted from electricity to sound for people to listen to.Sometimes, telecommunication systems are "duplex" (two-way systems) with a single box of electronics working as both a transmitter and a receiver, or a transceiver. For example, a cellular telephone is a transceiver. The transmission electronics and the receiver electronics within a transceiver are actually quite independent of each other. This can be readily explained by the fact that radio transmitters contain power amplifiers that operate with electrical powers measured in watts or kilowatts, but radio receivers deal with radio powers that are measured in the microwatts or nanowatts. Hence, transceivers have to be carefully designed and built to isolate their high-power circuitry and their low-power circuitry from each other, as to not cause interference.Telecommunication over fixed lines is called point-to-point communication because it is between one transmitter and one receiver. Telecommunication through radio broadcasts is called broadcast communication because it is between one powerful transmitter and numerous low-power but sensitive radio receivers.Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and to share the same physical channel are called multiplex systems. The sharing of physical channels using multiplexing often gives very large reductions in costs, Multiplexed systems are laid out in telecommunication networks, and the multiplexed signals are switched at nodes through to the correct destination terminal receiver.
Analog versus digital communications.Communications signals can be sent either by analog signals or digital signals. There are analog communication systems and digital communication systems. For an analog signal, the signal is varied continuously with respect to the information. In a digital signal, the information is encoded as a set of discrete values (for example, a set of ones and zeros). During the propagation and reception, the information contained in analog signals will inevitably be degraded by undesirable physical noise. (The output of a transmitter is noise-free for all practical purposes. ) Commonly, the noise in a communication system can be expressed as adding or subtracting from the desirable signal in a completely random way. This form of noise is called additive noise, with the understanding that the noise can be negative or positive at different instants of time. Noise that is not additive noise is a much more difficult situation to describe or analyze, and these other kinds of noise will be omitted here. On the other hand, unless the additive noise disturbance exceeds a certain threshold, the information contained in digital signals will remain intact. Their resistance to noise represents a key advantage of digital signals over analog signals.Telecommunication networks.A telecommunications network is a collection of transmitters, receivers and communication channels that send messages to one another. Some digital communications networks contain one or more routers that work together to transmit information to the correct user. An analog communications network consists of one or more switches that establish a connection between two or more users. For both types of network, repeaters may be necessary to amplify or recreate the signal when it is being transmitted over long distances. This is to combat attenuation that can render the signal indistinguishable from the noise. Another advantage of digital systems over analog is that their output is easier to store in memory, i.e. two voltage states (high and low) are easier to store than a continuous range of states.Communication channels.The term “channel” has two different meanings. In one meaning, a channel is the physical medium that carries a signal between the transmitter and the receiver. Examples include the atmosphere for sound communications, glass optical fibers for some kinds of optical communications, coaxial cables for communications by means of the voltages and electric currents in them, and free space for communications using visible light, infrared waves, ultraviolet light, and radio waves. Coaxial cable types are classified by RG type or “radio guide”, terminology derived from World War II. The various RG designations are used to classify the specific signal transmission applications. This last channel is called the “free space channel”. Sending radio waves from one place to another has nothing to do with the presence of an atmosphere between the two. Radio waves travel through a perfect vacuum just as easily as they travel through air, fog, clouds, or any other kind of gas. The other meaning of term “channel” in telecommunications is seen in the phrase communications channel, which is a subdivision of a transmission medium so that it can be used to send multiple streams of information simultaneously. For example, one radio station can broadcast radio waves into free space at frequencies in the neighborhood of 94.5 MHz (megahertz) while another radio station can simultaneously broadcast radio waves at frequencies in the neighborhood of 96.1 MHz. Each radio station would transmit radio waves over a frequency bandwidth of about 180 kHz (kilohertz), centered at frequencies such as the above, which are called the “carrier frequencies”. Each station in this example is separated from its adjacent stations by 200 kHz, and the difference between 200 kHz and 180 kHz (20 kHz) is an engineering allowance for the imperfections in the communication system.In the example above, the “free space channel” has been divided into communications channels according to frequencies, and each channel is assigned a separate frequency bandwidth in which to broadcast radio waves. This system of diving the medium into channels according to frequency is called “frequency-division multiplexing”. Another term for the same concept is “wavelength-division multiplexing”, which is more commonly used in optical communications when multiple transmitters share the same physical medium. Another way of dividing a communications medium into channels is to allocate each sender a recurring segment of time (a “time slot”, for example, 20 millisecond out of each second), and to allow each sender to send messages only within its own time slot. This method of diving the medium into communication channels is called “time-division multiplexing” (TDM), and is used in optical fiber communication. Some radio communication systems use a hybrid of TDM and FDM.