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Analog and Digital Signals
АНГЛИЙСКИЙ ЯЗЫК
Для студентов энергетического факультета
УЧЕБНОЕ ПОСОБИЕ
Рецензии написаны:
Кандидатом педагогических наук, заведующей кафедрой английской филологии ЕНУ им. Л.Гумилева Мейрамовой С.А.
Старшим преподавателем кафедры СГД университета «Туран» г. Астана Омаровой Б.И.
Старшим преподавателем кафедры мировых языков КАТУ им.С.Сейфуллина Байгашкаровой М.И.
Рассмотрено на заседании кафедры мировых языков, протокол № 9 от 28 мая2008 г.
Зав.кафедрой ________Туксаитова Р.О.
Учебное пособие по английскому языку для студентов энергетического факультета рассмотрено на заседании методической комиссии отдела гуманитарных кафедр протокол № 11 от 14 июня 2008 ж
Председатель методической комиссии___________Сергазина К.Ж.
Introduction
The wheel, which is thought to have been invented around 3500 b.c., was a tremendous technological advancement; without it or a similar invention, information probably would still be transported by people on foot or horseback, by smoke signals or drum sounds, by carrier pigeon. By now, however, people have refined the technology of motion to the point where mobility has become a way life.
The invention of the computer and its introduction into the business environment in the early 1950s marked a similar technological achievement. By the early 1960s, some information needed for business was available in computer-usable form “somewhere”; however, it may have been impossible or impractical to get it if the information needed was only available in a computer 1,000 miles away. Modern electronic communications – the movement of voice and data over long distances through the use of computers and telecommunications channels and equipment – has solved this problem.
You will encounter innumerable situations in the business environment that require data to be sent to, retrieved from, or shared among different locations.
To transmit or receive data, you must have special hardware – that is, a transmission method, as well as access to a telephone line or other transmission medium and special communications software on line at both sending and receiving locations.
When you are talking on the phone with another person who is a few houses away, you can probably hear that person clearly and do not need to speak loudly. However, sometimes the farther away you are from the person, the harder it is to hear clearly what is being said because of static and other noise. A lot of noise increases the chance that parts of your message will be garbled or misinterpreted. This same problem can exist when data is transmitting over phone lines from computer to computer. To overcome this problem, alternative types of computerized data transmission have been developed, including satellite and microwave – although they are not without their own limitations. And in this part of our text book we try to introduce you with common characteristics of communication means.
Part I
Telecommunication
Text 1
Analog and Digital Signals
Words and word combinations:
Continuous – непрерывный
a steady stream of water – постоянный поток воды
a garden hose – садовый шланг
is measured – измеряется
cycles per second – циклы в секунду
high-frequency sound waves – высокочастотные звуковые волны
low-frequency waves – низкочастотные волны
loudness – громкость
the short bursts of water – брызги воды
garden sprinkler – садовый разбрызгиватель
transmission medium – средства передачи
electrical pulses – электрические пульсы
digital data – цифровые данные
converting digital signals into analog – превращение цифровых сигналов в аналоговые
converting the analog signals back into digital – превращение аналоговых сигналов в цифровые
sending computer – отправляющий компьютер
receiving computer – принимающий компьютер
must be connected to a modem – должны быть соединены с модемом
both modems – оба модема
When we speak, we transmit continuous sound waves (fig.1), or analog signals, that form what we call ‘voice’. Analog signals could be compared to a steady stream of water coming out of a garden hose. These signals repeat a certain number of times over a certain time period- their frequency, which is measured in cycles per second, or hertz. Sometimes our voice sound high (composed of high-frequency sound waves) and sometimes our voices sound low (composed of low-frequency waves). Analog signals can also differ in amplitude, or loudness; a soft voice is at low amplitude. Telephone lines are currently an analog communications medium.
Continuous, or analog signal
Digital signals, in contrast, can be compared to the short bursts of water that shoot out of a timed garden sprinkler. These signals are discontinuous (discrete) pulses over a transmission medium (fig.2). Computers communicate with each other in streams of binary digits (bits) transmitted in patterns of digital signals- a series of on and off electrical pulses. For data to travel from one computer to another across the phone lines, the sending computer’s digital data must be converted into analog across the phone lines, the sending computer’s digital data must be converted into analog form and then recovered into digital form at the receiving end - modulation and demodulation.