More and more people are using mobile phones today. It is predicted that by 2010 there will be 2.5 billion mobile phone users worldwide.
Mobile phones are two-way radios that use radio frequency waves. That is a type of electromagnetic field (EMF) used to communicate information. The radio signal from the handset is transmitted through the air to the antenna (or aerial) of the nearest base station, which then passes the signal on to the network and through to its destination.
The building blocks of a mobile phone network are radio base stations that transmit and receive calls. The term 'base station' refers to the antenna fixed to the mast and connected to the radio transmission equipment stored in a secure cabinet. Each station covers a small area called a cell, hence the term 'cellular'. As radio waves reach only limited distances, mobile communication over a large geographical area requires a network of many base stations, with each station providing radio coverage over a particular area.
The mobile phone uses a SIM card for communication.
The SIM (Subscriber Identity Module) card holds a microchip and slips into the handset allowing you access to a mobile phone network. This network is made up of a series of base stations that send signals used by mobile phones. The area covered by each of these base stations is called a cell and cells overlap to make up a coverage area.
Whenever you switch a mobile phone on it will connect to the nearest base station. As you move around you may get closer to another base station in another cell. When this happens, the network will automatically switch your phone to the other base station.
If the base station that your phone is switched to is already working to its full capacity it cannot take in your signal. If this happens you may get a drop out and your phone will not work in that area. Dropped calls can also happen when you are in an area where cells do not overlap.
