Telecommunications satelliteTelecommunications is the sending and receiving of information using electricity, radio waves or light. The information can be data, sound or TV pictures. Data can represent text, sounds, images or video. Forms of telecommunications include the internet and other computer networks, phones, two-way radio and TV and radio broadcasting. Phone calls, text messages, emails and computer data—and often radio and TV signals as well—travel through a vast communications network.
All the different forms of telecommunications are turned into signals that can travel through the network. A network may be made up of telephone lines, cables, and radio and satellite links. Signal always travel between two points on the network (such as two mobile phones) and are directed through it by electronic switches. This is called a switched network. Radio and television networks, where signals are sent to many receivers from one transmitter, are known as broadcast networks.
A diagram of a telecommunications network
Wiring at a telephone exchange
All the telecommunications devices (telephones and home computers) connected to normal telephone lines are linked by the lines to a local telephone exchange. Each line has its own unique telephone number which the exchange uses to find it. All the local exchanges in one area are linked to a main exchange, which in turn is linked to other main exchanges to form a national network.
Also linked into the network are special exchanges for mobile phones, and internet service providers. Most information (speech and computer data) travels to and from the local exchange in analogue form and between local exchanges in digital form.
There are several different ways of linking a network together. Some links are underground cables, either in the form of electrical cables or fibre-optic cables, in which signals are carried by light. Some links are made with microwaves. International links across oceans are made via satellites in orbit around the Earth, and through cables stretched across the seabed.
Microwaves carry signals between hill-top transmitters and receivers, to and from communications satellites. Microwave transmitters and receivers are dish-shaped aerials. A transmitter focuses the microwaves into a narrow beam, which is aimed at a receiver that collects the waves. The microwaves are modulated (shaped) so that they can carry information.
The internet is a vast computer network that stretches right around the world, made up of hundreds of millions of computers. Information (text, pictures, video clips, etc.) can travel from any computer on the network to any other computer. The internet began in the 1960s, when research agencies in the USA built their own communications network. Other organizations, such as universities, gradually joined. As home computers became cheaper and more popular in the 1990s, the internet began expanding rapidly, with anybody being able to use it via a telephone line. Today, almost every computer in the world can connect to the internet, many now through wireless connections.
Using the internet
Internet use falls into two main areas: email and the world wide web. With email, it is possible to send a text message (with other data files, such as photographs, attached if needed) almost instantly to any other internet user at their email address.
The world wide web (the “web”) is a huge information-gathering system. It allows computer devices, including PCs, tablets, smartphones and others, connected to the internet to ask for and copy files from another device. The files are stored in standard form so that any computer can read them.
Other uses of the internet include phone calls, instant messaging and video calls, such as Skype.
Viewing Q-files on a tabletMost computers, tablets and smartphones are connected to the internet through internet service providers (ISPs), via broadband cables or mobile networks. Many homes and offices have a wireless network (Wi-Fi) linked to a broadband digital cable line, so that computers can connect to the internet without cables.
Consultant: Chris Oxlade
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