telecommunication introduction

Introduction


One way of understanding how telecommunications systems work and how they are changing is to consider a number of basic paired concepts. This short paper looks at nine such pairs and it should be emphasised that many of them are linked.


One-way v Interactive


Most broadcasting systems are one-way: the radio or television signal is transmitted to the listener or viewer and there is no means for the recipient to send back any information. By contrast, telecommunications systems – whether telegraph, telex, facsimile or telephony – are intrinsically two-way: both parties to the communication process have the same facility to send and receive the same kind of information. Increasingly, broadcasting systems are becoming more interactive as digital television allows viewers to use their sets to take part in electronic polling or order goods or send e-mail or access the Internet. Similarly more and more Web sites are becoming interactive allowing the user to comment on a film or book a play or order a book.


Analogue v Digital


Analogue signals have a continuous wave-like form. The further the signal travels, the more likely it is to become degraded and therefore, over anything other than short distances, these signals are boosted in strength at various points in the network and any subsequent distortions are amplified at the same time. By contrast, digital signals are discrete in form and essentially represent power on or off or – to use the binary language of computers – nought (0) or one (1). Digital signals can be recreated at their destination in exactly the form they left their starting point despite any distortion along the way, since the only two possibilities for the original signal are 0 and 1. All communications networks – whether telecommunications or broadcasting, whether fixed or mobile – are increasingly becoming digital because the quality of the signal is so much better and the capacity of the network is so much greater.

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