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Satellite Telephone Communication.
The new satellite telephone systems combine some of the attributes of cellular telephone systems with those of traditional satellite communications networks. Conventional cellular telephony uses a band of radio waves with frequencies between 800 and 900 million cycles per second (megahertz). (The newer personal communications services, or PCS, operate at about twice this frequency, but both systems function in the same manner). The area to be served is divided into "cell", each with a base station and radio tower. To keep the transmit and receive signals separate, cell phones transmit to the nearest base station on one frequency and receive from it on a different frequency.
The number of subscribers to cellular services has grown so large in the U.S. and elsewhere that systems are being upgraded with digital technology. In traditional networks the speaker's voice is impressed onto the transmitted radio wave by varying the wave's frequency, a technique known as frequency modulation. The problem with this method is that the transmitted signal entirely occupies a piece of radio-frequency bandwidth, or channel, that is 30 kilohertz wide. To provide more capacity, engineers are seeking to make more efficient use of the channels. Therefore, many systems are now being modified to operate with phones in - which the speaker's voice is converted to a stream of digital bits before being transmitted. The data can then be "compressed" prior to transmission, reducing the amount of time each transmission occupies the channel, at the price of a slight loss of signal quality.
Digital transmission of voice signals is also employed in the conventional (or "public switched") telephone network but at much higher rates - 64 kilobits per second, as opposed to the eight kilobits per second typical of digital cellular systems. Digital sampling at such a high rate ensures good quality but requires even more bandwidth that transmitting the analog signal itself. S why bother to do it? Because it affords an easy method of merging many telephone calls onto a single fiber-optic cable or microwave link, as the individual data streams can be multiplexed together into one, higher-rate stream, which in turn can be merged with others into still higher-rate streams. Also, with digital signals it is easier to remedy any impairment encountered in the network, because each bit can be restored if, for example, its amplitude were corrupted in some fashion.
The local central office switches are connected together (usually via fiber-optic cables) to even larger "toll" switches that handle the long-distance calls. Calls going overseas are routed to special international switches, from which they are then carried over undersea fiber-optic cables or via satellite.
Вариант 4.
Задание 1. Измените число существительных с единственного на множественное и внесите соответствующие изменения в остальные члены предложений.
1. I sow a boy in the street.
2. Don't sign the contract.
3. The director is out.
4. A sales representative must be acreative person.
5. He is a businessman.
6. He became the president of a big company.
Задание 2. Измените форму прилагательных, данных в скобках, и переведите предложения на русский язык.
1. My dog is (good) than yours.
2. My dog is the (good) of the three.
3. The cat will be much (happy) in hernew home.
4. My cold is (bad) today than it was yesterday.
5. This mountain is the (high) in Europe.
6. This piece of homework is as (bad) as your last one.
Задание 3.Вставьте модальные глаголы may, can, must, need.
1. I... have thrown the letter away.
2. ... you type?
3. It... be (have been) him.
4. You ... come at 6 o'clock.
5. ... I come in?
6. ... I see your license?
Задание 4. Поставьте глаголы, данные в скобках, в нужную форму.
1. We (to look for) someone who (to wont) to make money.
2. It's the best book I (ever to read).
3. It (to grow) dark, so we (to decide) to return.
4. He said that he (shall) go to the cinema.
5. I (study) grammar last year.
6. He said that he (be) working hard.
Задание 5. Переведите предложения на английский язык.
1. Сообщите нам, сможете ли вы принять участие в этом состязании.
2. Кто хочет пойти с ними? – Мы все хотим.
3. Наши мечты могут осуществиться.
4. Снег растает, как только выглянет солнце.
5. Мне кажется, вам не интересен этот предмет.
6. Джон не может этого сделать, и вы тоже не сможете.
Задание 6. Образуйте отрицательную и вопросительную формы предложений.
1. I have been studying English for 2 years.
2. He has just flown over Great Britain.
3. She studies English words before she goes to bed.
4. He is writing now.
5. My sister has read this magazine.
Задание 7. Задайте вопросы к каждому члену предложения.
1. American high school students like to use computers.
2. The man with the magazine in his hands is standing next to the counter.
3. The boy is playing in front of his parents.
4. We are taught science and biology.
5. The train will leave at 1:35 p.m.
Задание 8. Задайте общий, специальный, альтернативный и разделительный вопросы к каждому предложению.
1. I have a good sense of humor.
2. I've been a subscriber to "Click" magazine since January 1993.
3. It was a beautiful spring evening.
4. My parents had come to Paris a week before I arrived.
5. One days ago I bought a cassette player.
Задание 9. Переведите текст на русский язык.
MESSAGES BY ELECTRICITY.
Electricity completely changed communications. Once it was discovered that an electric current would flow along a wire, it seemed possible that it could be used for message. As long as two places were connected by a wire electric currents could be sent along it. They could be sent with the speed of light. The question was how could electric current make words?
Real telegraphs were not possible until it was proved that electricity and magnetism were connected. It was found that a needle of a compass moved when it was put near a wire with a current flowing through it. A compass needle is a magnet. If a wire carrying a current could move it, then the wire must be a magnet too.
A lot of people began to see how electro-magnets could be used to send messages. One of the most famous people of all in communication is Samuel Morse. He invented the Morse code. This code is still used in signaling all over the world. His idea was simple. He thought of using time, sending, current along a wire for a long time or a short time. Combining different sets of these "impulses", just using the long or short, he made a code for the whole alphabet, and the numbers from 0 to 9.
The Morse code simplified sending messages. It was also very fast. With practice, the Morse code can be read at 30 words a minute or more. It became the most widely used code because it was the easiest to understand and the fastest to transmit. The telegraph meant that at last people could send messages a long way at great speed. Soon people wanted to send messages even farther.
If two places on land, say, London and Manchester could be connected by wire, why could not the lands themselves - England and America, for instance, be connected by wires under the sea? This was a question quickly answered after the telegraph was proved to work. There were some problems about this, however. The main one was insulation, which means protecting the wire so that electric current does not leak away. Dry air is a good insulator, but sea water is not. If a wire was laid under water, the current would all leak away. In any case, all the insulating substances, known up to then could be damaged by sea water. But in 1847 gutta-percha was introduced as an insulating material. Gutta-percha is a gummy substance obtained from trees, like rubber and it does not allow electricity to flow through it easily.
Вариант 5.
Задание 1. Измените число существительных с единственного на множественное и внесите соответствующие изменения в остальные члены предложений.
1. This is my Study.
2. It is not a bad egg.
3. He took off his hat.
4. My tooth is white.
5. This isn't a mouse.
6. What colour is the box?
Задание 2. Измените форму прилагательных, данных в скобках, и переведите предложения на русский язык.
1. Asia is (large) than Europe.
2. Which is the (big) planet in the solar system?
3. This is the (short) way to the station.
4. The cat a (fat) than the kitten.
5. You are a (happy) boy!
6. Which is the (small) planet in the solar system?
Задание 3.Вставьте модальные глаголы may, can, must, need.
1.... he ride a bike?
2. If you want to be healthy, you ... drink much coffee.
3. ... I take a sweet? Yes, of course.
4. You ... choose any instrument if you like.
5. You ... learn music.
6. ... I listen to the music?
Задание 4. Поставьте глаголы, данные в скобках, в нужную форму.
1. If you (not to listen) to the radio, please (to switch) it off.
2. Somebody (to drink) my coffee! My cup was full.
3. The robbers (to steal) the car and they (to drive) away.
4. But last January I (to read) a book about Russian travelers. ,.
5. We (to live) next door to each other since Alison (to move) to London.
6. Dan (to get) a fax from Boston an hour ago, but he not (to answer) it yet.
Задание 5. Переведите предложения на английский язык.
1. Сколько тебе было лет, когда ты начал учить французский?
2. Переписывая это упражнение, обратите внимание на незнакомые слова.
3. Она училась музыке, когда жила в Париже.
4. Я купил эту картину в Лондоне.
5. Она опоздала на поезд.
6. Что вы делали все утро?
Задание 6. Образуйте отрицательную и вопросительную формы предложений.
1. His dad was an architect.
2. He went to the pond.
3. They noticed that the sun had gone down.
4. She was very beautiful.
5. My friends know all the best places to go.
Задание 7. Задайте вопросы к каждому члену предложения.
1. I always drink orange juice in the morning.
2. We have English lessons twice a week.
3. He was on vacation in Moscow with his family.
4. We’ve been playing games together all the time.
5. They collect stamps and coins.
Задание 8. Задайте общий, специальный, альтернативный и разделительный вопросы к каждому предложению.
1. Most English and Americans don't understand each other quite easily.
2. They are playing games.
3. He has been drinking juice since childhood.
4. I'm translating a text from a textbook.
5. We usually translate two texts a week.
Задание 9. Переведите текст на русский язык.
Telegraphy.
Electricity completely changed communications. Once it was discovered that electric current flows along a wire, it seemed possible that it could be used for messages. As long as two places were connected by a wire electric impulses could be sent along it. It meant that people were able to send messages a long way at great speed. The new way of communication had a lot of advantages and by the end of the 19th century cables were laid all over the world.
Samuel Morse, one of the most famous people in communications, invented a special code, which we call now "the Morse code". He thought of using short and long electric impulses. Combining different sets of impulses he made a code for the whole alphabet, and the numbers from 0 to 9. This code, was the easiest and the fastest to transmit.
Later on the necessity aroused to increase the speed of sending messages. People decided to use the fact that current could flow one way round the circuit or the other. A new system called double current working" was worked out According to this system a dash and a dot are impulses of the same length but of different directions.
Then a machine was invented to send typewriter messages over a telegraph circuit. Such machines are called teleprinters or teletypes and use International 5-unit code instead of the Morse code. Each letter or figure is made up of five impulses of electric current, either positive or negative, all letters being the same length in time. A teleprinter has a keyboard and every- time one of the keys on the keyboard is pressed it sends the five impulses that make one letter or figure.
As most modern systems use alternating current, one line can be used to send many messages at the same time. It is possible if each message is sent out at a different frequency. This allows high-speed telegraph communication as well as transmission of written messages.
Вариант 6.
Задание 1. Измените число существительных с единственного на множественное и внесите соответствующие изменения в остальные члены предложений.
1. The roof of that house leaks, it needs repairing.
2. The child saw a sheep in the field.
3. A passer-by saw the accident.
4. Put this knife on that table.
5. He is putting on his coat.
6. This program will be shown by him.
Задание 2. Измените форму прилагательных, данных в скобках, и переведите предложения на русский язык.
1. His dog is (good) than yours.
2. This is the (wonderful) and (beautiful film I have ever seen.
3. Tom is (tall) than Richard.
4. The train goes not as (fast) as an airplane.
5. The cat is (much happy) in her new home.
6. Henry is the (old) of the three brothers.
Задание 3.Вставьте модальные глаголы may, can, must, need.
1. Shall I write a letter to him? - No, you ... not, it is not necessary.
2. We... not carry the bookcase upstairs: the workers will come and do it.
3. ... we do the exercise at once? - Yes, you ... do it at once.
4. You... take any book you like.
5. A feel... ask more questions than a wise man... answer.
6. What time is it? It... be about 6 o'clock, but I am not sure.
Задание 4. Поставьте глаголы, данные в скобках, в нужную форму.
1. I (tell) you the answer yesterday.
2. He (arrive) at 12 o'clock.
3. You (lock) the door before you leave house?
4. I (read) this book when I was at school.
5. He usually (live) with family for six month every year.
6. I (leave) home at 8 .00 and (get) here at 15.00.
Задание 5. Переведите предложения на английский язык.
1. Мой друг сказал, что его брат уже приехал.
2. Гарри делал свою работу, пока его друзья играли в карты.
3. Я спросила у него, почему он не ответил на мое письмо.
4. Мария обычно очень внимательно слушает своего учителя.
5. Моя шляпа слетела, когда я шел по мосту.
6. Он смотрел в окно, когда я вошел в комнату.
Задание 6. Образуйте отрицательную и вопросительную формы предложений.
1. He had done his lessons by 5 o'clock.
2. They enjoy working with the computer.
3. Our friend knows Spanish very well.
4. She will return home later than usually.
5. I was repairing my car the whole day yesterday.
Задание 7. Задайте вопросы к каждому члену предложения.
1. He has just translated this article.
2. They will have done this work by 11 o'clock tomorrow.
3. Jane translated a lot of foreign letters at the office last week.
4. We were inventing to stay at castle for a night
5. Although the weather was fine they decided to stay at home.
Задание 8. Задайте общий, специальный, альтернативный и разделительный вопросы к каждому предложению.
1. It is winter.
2. There were three mistakes in my text.
3. Our friend often invents us to the parties.
4. If I don't pass the exams I'll try to do it again next time.
5. He often reads detective stories.
Задание 9. Переведите текст на русский язык.