How Do Mobile Phones Work?

Mobile phones work using "cells". Each cell has a base station at its centre. The base station sends and recieves calls from your phone. Your phone communicates with the base station using radio waves.
As your phone moves from cell to cell, your calls are transmitted from the nearest base station.

The size of mobile phone cells varies. In the country there is one base station every 10Km, but in towns they can be separated by only 500m. Each base station can only handle a limited number of calls. Since in a city many people may be making calls at once, many base stations are required to handle them.

The power of the base station transmitters must be be carefully worked out to avoid interference. To avoid this, cells are grouped in "clusters" in which each base station uses a different frequency - represented in the diagram as different colours. These frequencies are then re-used in neighbouring clusters.