How mobile phones work is interesting, but a little complicated to explain. To help you, I'm going to explain what happens when you pick up your phone and make a phone call.

So you've got your phone in your hand. I'm sure you know that the signal bars on the screen indicate how good a signal your phone is getting. What determines this is how close you are to a base stationthat is, an antenna that is connected to a real, wired phone network.

Base stations are the core of a mobile phone network, and there are a lot of them. In a city, they can be as little as a quarter of a mile apart, and even far out in the countryside there tends to be one every five miles or so. You don't tend to see them, because they're cleverly disguisedoften inside church towers, sometimes even posing as treesbut they are absolutely everywhere.

In reality, when you pay your mobile phone bill, it's these antennas that you're paying forand if you campaign against having a new one built near your house, the chances are that you're campaigning against your own phone signal.

Wherever you are, then, there's an antenna nearby for you to connect toif there isn't, or if you're out of its line of sight (underground, for example), then you get no signal and can't make any calls. When you move out of range of one base station, it quickly notifies the next one along to look out for you, allowing you to move quickly between areas without losing your signal for even a second. That's why the networks are known as 'cellular': it's because a lot of individual parts make up an unbroken network, just the same way as a huge number of cells make up your body.