In the central switching hub pictured here, several telephone connections are made. Despite technological advances, telephones in a large office building still have to be manually connected together with wires. As in this photograph, this process may involve hundreds of telephone cables.
Mobile (cellular) phones have become invaluable for people who need to stay in touch while on the move. Cellular telephone systems combine radio and television technology with computer systems. As a caller moves from one geographical cell (the name given to a specific part of the area being covered by the system) to another, computers in switching offices transfer calls among variously located antenna transmitters without interrupting service.
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