Mobile phones, which are properly called cellular phones, allow calls to be made wherever the caller happens to be. They are called cellular phones because a territory is divided up into a series of small areas, or cells, each with a small radio station. When a call is made, the telephone sends a radio message to the base station, which in turn passes it to a mobile phone exchange. Here the signal can be routed to the ordinary telephone system, or transmitted back to another mobile phone. Mobile phones use low-powered microwaves to send and receive messages to and from the base station.
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