2 Read the text

Communications

User often want to send messages from one network to another or to computers on the other side of the world. This can be done using a variety of communication links. Normal copper telephone wires can be used over short distances but shielded cable called coaxial cable or coax can be used for longer distances. However, coax has largely been replaced by even faster cable known as fibre optics or fibre optic cable. (Note that the American spelling of fibre is fiber.) Fibre optic cable uses glass fibres to conduct a beam of laser light. To transmit signals long distances around the world satellites are often used. The signal is transmitted and received by earth-satellite stations positioned at suitable locations over the earth’s surface. Microwave transmissions are another means of transmitting signals from one microwave station to another.

An increasingly popular way of communicating using computers is voicemail. In this system, spoken messages are sent to a server computer where they are stored in areas called voice mailboxes. When the user connects to their mailbox they can listen to the stored messages.

Video conferencing is a more advanced form of communication by computer, which enables meetings to take place over long distances. Video cameras are used at each end of the communications link so that the participants can see and hear each other. The end of the link nearest a user is called Near End and the end of the link furthest from the user is called Far End. Each user has a keypad that enables them to control features of the system, for example to make or end a call, adjust the sound volume, and zoom the camera in to get close-up views, or zoom it back for a broader perspective. An additional display feature, called picture-in-picture, allows one image to be displayed inside another image.

When a piece of text is scanned using a scanner input device, an image of the text is input to the computer and displayed on the screen. It is not possible to change or edit the displayed text using a word processor, however, because the image is graphical, not digital. An optical character recognition (OCR) program must be used to convert the text image into digital text characters that can be edited. To identify a scanned text character, the software compares the caracter image to stored data about the shape of standard characters. It is easier for the OCR software to recognize the scanned characters if they are printed using block capitals and are not too small. If a text is written in ‘joined-up’ writing, it is more difficult for the OCR to identify because there are extra lines and loops between the letters.

3 Answer the following questions:

1 In what way can users send messages from one network to another or to computers on the other side of the world?

2 What means are usually used to send messages over short and long distances?

3 What has coax largely been replaced by?

4 What are the world satellites used for?

5 In what way does the voice system operate?

6 What is the most advanced form of communication?

Test 8

Match each word from column A (1-20) with its partner from column B (a-u) to make a computing term definition from Basic English for Computing Unit 12

A	B
1voicemail	a)a storage area for spoken messages
2 video conference	b) a form of communication over a network that uses video cameras so that the people taking part can see and hear each other
3 fibre-optic cable	c) an installation for receiving and transmitting microwave signals
4 send	d) an object which has been sent into space in order to collect information or to be part of a communications system. It moves continually round the earth or around another planet
5 transmit	e) a switching device, that being under voltage loops and disconnects one or more electric circuits. It was widely used in early electromechanical computers
6 coax(ial) cable	f) the process of sending a high frequency signal known as microwave
7 communications link	g) a signal that can only have one of two values representing on or off
8 earth satellite station	h) the process of sending a signal to, or receiving a signal from, a satellite orbiting the Earth
9 Far End	j) a type of signal that can take any value between a maximum and minimum
10 microwave station	k) a display screen feature that has a video picture displayed inside another video picture
11 microwave transmission	l) the equipment at the closest end of a video conferencing system
12 P-I-P (picture-in-picture)	m) the equipment at the remote end of a video conferencing system
13 Near End	n) an installation on Earth used for sending and receiving signals to or from a satellite
14 earth-satellite transmission	o) a connection between two points for transmitting and receiving signals
15 digital signal	p) a type of shielded cable for carrying signals. It is often used with radio frequency and video signals
16 analogue signal	q) cause something to pass on from one person or place to another by means of communication
17 relay	r) take something to a particular destination or arrange something for the delivery, especially by post
18 earth satellite	s) a cable made from strands of glass that is used for carrying information signals on a beam of light
19 video conferencing	t) a meeting between people that are a long distance apart using cameras and display screens connected to a network to allow the people to see and hear each other
20 voice mailbox	u) a system of communication that uses computers to store spoken messages

Unit 13