MOBILE PHONE SERVICE MOVES AHEAD.

Advanced Mobile Phone Service (AMPS) is an economical mobile telephone service based on efficient use of the available radio frequency spectrum. It is a cellular system - that is, it divides a service area into subparts, or cells. Each cell is served by low-power transmitters, separate receivers, and a control system. This combination of equipment is called a ″cell site.″ The available radio channels - up to 666 of them in the 850-MHz frequency band - are allocated among the cell sites. Different channels are assigned to neighboring cells to avoid interference, but channels assigned to one cell site can be reused at another cell site in the service area, as long as the sites are far enough apart to prevent interference. Channels may be used simultaneously 20 or more times in an urban area.