4.1.2 The network

The network is a communication channel in that it conveys data from the transmitter to the receiver. The network may also manipulate data in some way, and it may also store or retrieve data.

In a mobile phone system, the network conveys the message from User l's handset to User 2's. It will also store the identity of User 1 and the duration of the call. This data is used to work out the amount to charge User 1, which is a form of manipulation of data. A network can be very complex, so a call does not usually go directly from one caller to another in a single step. The network, therefore, will select the route for conveying a call through the network from the transmitter to the receiver.