A telecommunication system in which a number, often a large number, of transmitters are spread over a wide region to enable a mobile radio system to operate anywhere within that region. The radio system will first decide which transmitter provides the greatest signal at a particular point; it will then transmit to and receive from that transmitter until the signal becomes weak, when it will attempt to transfer to the transmitter that now provides the greatest signal. The radio system may be a mobile phone or a mobile multimedia system comprising personal computer and transmitter; where the system is designed for stand-alone personal use it is sometimes referred to as a personal communications device. The transmitters may be at fixed land-based sites, connected to a main telecommunications network, such as the telephone system, by means of land lines or microwave link; alternatively they may be satellite-based, in which case the signal is then relayed to another earth-based station.