1. Introduction

Communicating is tranferring information from one person or location to another. There are many different methods that can be used to communicate information. The best method to use on a particular occasion will depend upon factors such as :

1. What type of information you are sending, e.g. a package, a document or a video.
2. How quickly the information must arrive at its destination.
3. What equipment you have to help you send the information and what equipment the person receiving the information has.
4. How much you are prepared to pay to send the information.
5. Whether the information is private and being sent to just one person or public and being sent to many people.

Communications systems can be classified as being either private or broadcast. Private systems are used for private communications between a small number of people. Broadcast systems allow one person to send the same information to lots of people at the same time. Some of the most common communication systems are listed below.

Private Communications Systems
Post
Telephone
Cellular Telephone
Fax
Email
Video Conferencing
Broadcast Communications Systems
Teletext
Digital TV

Data can be communicated directly between computers through a computer network or using a modem or ISDN.

2. Post

The traditional postal system can be used to deliver letters and parcels to almost anywhere in the world. This is because a postal system is simple to operate and requires virtually no modern technology to function.

An address written on a package is used to identify the destination to which it should be delivered. Most countries include a code such as a postcode in the address. This identifies the area that the package is to be delivered to. If a computerised sorting system is available then this will use the code to automatically route a package to its destination. The last stage of delivery is carried out by a postman who takes the package to the house that it is addressed to.

The cost of sending a package is paid for by purchasing stamps which are stuck onto the packet. It is more expensive to send heavier packages. It also costs more to get a package delivered more quickly.

3. Telephone

A telephone network enables instant voice communication between two people. All countries have a telephone network but the proportion of people who have access to a telephone varies from country to country. In the UK over 95% of people have a telephone at home.

People who use a telephone system are known as subscribers. Each telephone connected to a network is identified by a unique number. To start a conversation with another person on the network you must dial the number of the person's telephone. A modern telephone system relies on a lot of highly sophisticated computer equipment to manage and connect calls.

Subscribers have to pay to use the telephone network. This payment consists of a fixed monthly charge for connection to the network and call charges. The cost of a call depends upon the length of the call, the time of day at which it is made and the distance between the people making and receiving the call.

The telephone network can also be used for transmitting data with a modem or for sending faxes. In the UK more than half of the capacity of the telephone network is now used for sending data.

4. Cellular Telephones

Cellular telephones perform the same functions as an ordinary telephone. They can be used for instant voice communications with another person. By dialling the number of another cellular telephone you can instantly talk to the person who owns it. Over 30 million cellular telephones have been sold in the UK.

Ordinary telephones are connected to the telephone network by cables which run under and above the ground. Because of this a telephone can not be moved around. It can only be used near the point at which it connects to the network. In contrast a cellular telephone connects to the telephone network using radio waves. A cellular phone can be moved around and used at any point that is covered by the network. Most cellular phones can be used anywhere within the country they are purchased in and can often be used abroad as well.

Data can be transmitted using a modem and a cellular phone but this transmission is much slower than sending data with an ordinary phone. You can send text messages from one cellular phone to another using a system called Simple Messaging System (SMS). WAP phones let you access some Internet sites so that you can get useful text information such as traffic news via your phone. More similar services will be introduced now that faster GPRS phones are available.

There are many different ways that you can pay to use a cellular phone. Whichever way you choose, it is normally more expensive to use a cellular phone than an ordinary phone. There is a continuing debate over the safety of cellular telephones. Some surveys suggest that the radiowaves transmitted and received by these phones might affect brain activity.

5. Fax

A fax machine can be used to send copies of documents from one location to another. A fax machine consists of a scanner, printer and modem all built into one device. The document that is to be sent is inserted into a fax machine. It scans the pages and sends them via the telephone network to another fax machine. The receiving fax machine then prints a copy of the document.

A fax machine can be connected to the telephone network just like a telephone. A fax machine is identified by a number which you must dial to send a document to it. Few people have fax machines at home but most businesses have a fax machine. Charges for sending faxes are set in the same way as for making telephone calls.

6. Email

Electronic Mail (email) is a system which allows users of a computer network to send messages to each other. Users can usually :

• Send a message to another user, or group of users (whose names are on a mailing list).
• Keep their messages in a mailbox.
• Read, print and delete messages from their mailbox.

Each user has to have his or her own address that other users need to know to send messages to him or her. An example address is :

mark@mwchemicals.co.uk

An email system can transmit other types of information as well as simple text. Pictures, music, videos, in fact almost any sort of information that you can think of can also be sent. This is achieved by attaching files created in another package such as a word processor or drawing program to the end of an email message. These files are known as attachments.

An electronic mail system can be private and only operate within a particular company on the company's own WAN. However most email is now sent via the Internet so that any Internet user can send and receive email. In the year 2000 approximately one quarter of the UK population could send and receive emails. In poorer countries the proportion of people with access to email is much lower.

The cost of sending an email is very low. It is much cheaper to communicate by email than by post, fax or telephone. This is especially true if the person you are communicating with lives a long way away.

7. Video Conferencing

Video conferencing uses the telephone network to transmit video images from one location to another. These video images can be transmitted and received by computers with cameras attached or by specialised video conferencing hardware.

Video images can not be sent down a single telephone line. Usually many lines are required at the same time to send a high quality video picture, so using video conferencing is expensive.

Video conferences can take place between just two people. Frequently however many people, all at different locations, take part in a video conference at the same time. Large companies often use video conferencing systems. It can be much cheaper to hold a video conference than to bring a lot of people together to hold a normal conference. This is especially likely to be true if the people involved in the conference work a long way away from each other.

Video conferencing can be achieved much more cheaply by using web cameras on the Internet, but the picture quality will not be as good. An even cheaper solution to hold a meeting between people at different locations is to use teleconferencing. In a teleconference only sound is transmitted. A teleconference is effectively a telephone call but with many people taking part in it instead of just two.

Advantages	Video conferences can bring a large number of people together to hold a conference without them having to travel. This can save money. Live video pictures can be sent during a video conference.
Disadvantages	The quality of transmitted video images is not usually very good. It is much more expensive to hold a video conference than to talk on the telephone. You need specialised equipment to hold a video conference.

8. Teletext

The teletext system transmits text and very simple graphical information to televisions. To access teletext you need a television set with a teletext decoder built into it. Each television channel can provide its own teletext service. The channel supplies the information that is included on the service.

Teletext information is sent as pages, each of which is identified by a three-figure number such as 100 or 360. The pages are transmitted in sequence, one after the other. To access a particular page you must enter the page's number into your television using a remote control. You will then have to wait until the page that you want is next transmitted. When this occurs the page will be displayed, but you may have to wait for as long as a minute to view a particular page.

Typical information that is available on a teletext system includes news, weather, television listings, financial news and sports reports. Deaf people can use teletext to put subtitles at the bottom of the television screen so that they can read the words that are being spoken.

9. Digital Television

Digital television was introduced in the UK in 1999. Eventually the digital television system will replace the current analogue system. Digital television has a number of advantages over analogue television. In particular :

1. Many more channels can be broadcast at the same time using digital television than using analogue television.
2. Digital pictures suffer less from interferance that analogue pictures.
3. Digital pictures can be transmitted in a range of formats such as widescreen.

To receive digital television you must either purchase a special decoder or a new television with a decoder built into it. Digital television can be received by satellite, radio waves or fibre-optic cable. Most digital television decoders also include a modem which can be used to connect the decoder to the telephone network so that data can be sent from the viewer back to the television channel. This enables the provision of interactive television where the user can influence what is transmitted.

The companies that run digital television channels have used the capabilities of digital television to provide a range of new services such as :

Digital televisions integrate a number of different functions from broadcasting and telecommunications into one product. It is likely that further integration of different communications technologies will take place in the future.

GCSE ICT Companion 04 - (C) P Meakin 2004