1.What are telecommunication networks?

    Before we start talking about the radio or the Internet  we have to explain what do we exactly mean by "telecommunication networks", in order to make sure that we have a clear idea about this concept.  There are lots of different networks, each of them integrated by diverse elements and with different uses. However, we could say that, in general terms, a telecommunication network is made up by several links and nodes that enable communication between two or more terminals  in long distances.  Depending on the network we are talking about, there will be different types of terminals, links, nodes..., concerning the uses  the network might have, the distance that separates the terminals, the number of terminals de communication is directed to, the kind of communication we want to send or receive, etc.

Nowadays, telecommunication networks are integrated by complex structures and elements such as satellites or big terrestrial stations, which enable communication from one pole to the other. But, of course, it hasn't always been like that. In the last hundred years they have appeared some revolutionary networks which have even changed our habits and which have made our daily-life easier than never before.  As  clear examples of this, we should mention the impact that networks such as the telephone, the radio or the television -which have reached billions or users all over the world- have made in society. But, of course, this is nothing compared to the huge revolution that the appearance of the Internet meant in the telecommunications field.