Химия C. Text Study просмотров - 191
B. Text Study
I. Look at the title of the text. Make your predictions about the contents of it. Read the text and answer the questions.
1. What is the origin of the term “modem”?
2. What kind of device is a modem?
3. What are the names of the two main types of modems?
Modem is a device that enables computers, facsimile machines and other equipment to communicate with each other across telephone lines or over cable television network cables. In the strictest sense, a modem is a device that converts between analog signals, such as sound waves, and digital signals, which are used by computers. However, the term has also come to include devices that permit the transmission of entirely digital signals.
Modems transmit data at different speeds, measured by the number of bits of data they send per second (bps). A 28.8 Kbps modem sends data at 28,800 bits per second. A 56 Kbps modem is twice as fast, sending and receiving data at a rate of 56,000 bits per second.
An analog modem converts between the digital signals of the sending computer to analog signals that can be transmitted through telephone lines. When the signal reaches its destination, another modem reconstructs the original digital signal, which is processed by the receiving computer. A standard analog modem has a maximum speed of 33.6 Kbps.
The word modem is an acronym formed from the two basic functions of an analog modem: modulation and demodulation. To convert a digital signal to an analog one, the modem generates a carrier wave and modulates, or adjusts it according to the digital signal. The kind of modulation used depends on the application and the speed of operation for which the modem is designed. The process of receiving the analog signal and converting it back to a digital signal is called demodulation.
Cable modems permit the transmission of data over community antenna television (CATV) networks — that is, the network of cables used to distribute cable television. A cable modem transmits data from the network at about 3 Mbps and transmits data to the network at between 500 Kbps and 2.5 Mbps.
Like a standard analog modem, a cable modem converts between a digital signal and an analog signal. Cable modems are much more complex than standard analog modems. They also incorporate a tuner that separates the digital data from the rest of the broadcast television signal. Because users in multiple locations share the same cable, the modem also includes hardware that permits multiple connections and an encryption/decryption device that prevents data from being intercepted by another user or being sent to the wrong place.
II. Read the text and define whether the following statements are true or false.
1. A modem links computers by means of ordinary telephone lines.
2. Modems convert a computer’s analog language into digital signals that can be transmitted via telephone cables.
3. The device is called “a modem” in honour of its inventor.
4. The process of converting analog signals into digital is called modulation.
5. Analog modems are more complicated than cable ones.
III. Expand the sentences.
1. A modem allows computer to communicate via telephone lines.
2. Modems transmit data at different speeds.
3. There are two main kinds of modems – analog and cable ones.
IV. Now decide which of the following statements express important ideas or supporting details.
1. a) Modem speeds are measured by the number of bits of data they send per second.
b) A modem allows fast transmission of data to other computers over distances.
c) A 28.8 Kb ps modem sends data at 28.800 bits per second.
2. a) Information travels through the Internet divided into “packets” of data that take different routes.
b) Byte is a unit for measuring the amount of information stored or processed by a computer.
c) The speed of data transmission by means of modem is measured in bits per second.
3. a) An analog modem converts between the digital signals to analog signals that can be transmitted through telephone lines.
b) Cable modems send and receive information over the network of TV cables.
c) There are analog and cable modems.
V. Find the words – carriers of the primary and the secondary information in paragraph 3.
VI. Define the function of commas in paragraph 1.
VII. Find out the means of connection of simple, compound and complex sentences
VIII. Arrange the sentences in the logical order according to the text.
1. Cable modems permit the transmission of signals over CATV networks.
2. Another modem reconstructs the original data when the signal reaches its destination.
3. A modem converts between analog and digital signals.
4. The term is an acronym formed from 2 basic functions of an analog modem.
5. A maximum speed of an analog modem is 33.6 Kbps.
6. Cable modems incorporate tuners, hardware for multiple connections and encryption/decryption devices.
IX. Give the main points of the text in 4-5 sentences.
I. Translate from English into Russian.