Read the text and translate it in a written into Ukrainian using a dictionary.

Data transmission

A terminal or computer produces digital signals, which are simply the presence or absence of an electrical pulse. The state of being on or off represents the binary number 1 or 0. Some communication lines accept digital transmission directly, and the trend in the communications industry is toward digital signals. However, most telephone lines through which these digital signals are sent were originally built for voice transmission, and voice of transmission requires analogue signals. We look at these two types of transmission and study modems, which translate between them.

Analogue transmission. The older telephone system function on the basis of analogue signals representing voice modulation patterns which are represented by variations in wave forms. When using telephone lines for transmitting data by terminal to a computer, the digital signals from the terminal need to be converted to analogue signals by an acoustic coupler or modem prior to transmission. A modem is a device which serves a dual purposes because it acts as a MOdulator (digital to analogue) and DEModulator (analogue to digital), hence the name MODEM. An analogue communication system requires a modem at either end of the communication line. When the signals are received by the distant computer, the signals are reconverted to digital form prior to being input for processing.

Digital transmission. Analogue transmission has been in use for many years as the basis of telephone technology and is very effective for this purpose, but it is not so suitable for high-speed transmission of information. Digital transmission consists of electrical pulses representing data in binary code as a series of on/off pulses. A number of different codes exist, some of which are based on a 6-7-, or 8-bit structure. ASCII is a 7-bit code and EBCDIC is an 8-bit code. The codes represent characters, transmission control signals, information separators, and device control. Digital technology has a number of advantages compared to analogue, including higher transmission speed, lower incidence of errors, and the facility for mixing data consisting of voice, image, and text on the same circuit. It is for this reason that data transmissions will be increasing digital in the future.

 

Make up a plan in the form of questions.

 

IV. Comprehensive skills

Read and remember

jack	- штепсель
coupler	- зчеп, зчіпка, з'єднувальний пристрій, зчіпна муфта

Listen to the text “Modems” and try to understand it.

 

True or false statements.

1. A modem can demodulate the analogue signal.

2. A modem is a device that allows remote computers to communicate, to transmit and receive data using telephone lines.

3. An internal modem boards can not be installed in a personal computer as standard equipment.

4. The advantage of an external direct-connected modem is that can be connected to any phone, but the transmission quality may suffer since they are not connected directly to the telephone line.

 

Listen to the text once again and answer the following questions.

1. What are the main two types of modem? (according to the text)

2. What type of modem is more preferable for portable PC? (according to the text)

 

 

V. Communicative skills

Ex. 1 Complete the dialogue using the following words.

carriers competition deregulation fee hooked up installed monopoly suburbs telecommunications to place calls

 

Sandra: Tony, I just moved into my new apartment, and I need to have the phone ___. I have no idea what I am doing; I have to make all these decisions about local, local long-distance, and long-distance ___.

Tony: I know - it's really complicated. In America, we have somewhere between five and ten thousand long-distance telephone companies. It's good for ___, but sometimes I think we have too much choice! It was easier before ___in the early eighties. The ___industry has become far too confusing, but at least prices have really gone down in the last twenty years.

Sandra: Why do I need to choose more than one company?

Tony: We divide telephone service into three categories: local, local long-distance, and long-distance. Your long-distance company allows you to call foreign countries, other American states, and other cities in your state. Your local long-distance company allows you to call ___ or regions just outside your city. And, of course, your local company allows you ___ within your own city.

Sandra: But they only asked me to choose a local long-distance company and a long-distance company. Don't I get to choose my local service?

Tony: In Southern California, we really don't have much choice yet when it comes to local service. It's still basically a ___.

Sandra: Is it really expensive to make local telephone calls then? How much does it cost per minute?

Tony: Actually, for most people, local calls do not have a per-minute charge. You pay your local telephone company a monthly service ___ of around ten to fifteen dollars for your local service, but then you don't have to pay per minute.

Sandra: You don't pay per minute? That's amazing! In my country, I normally have to pay a lot of money for local calls.

Tony: I rarely pay more than twenty dollars a month for local, local long-distance, and long-distance combined. It's so cheap that I had an extra telephone line ___ for my daughter.