How the Cellphone System Works…

Every cellular system digital or analog is comprised of four parts.

1) Cells and cell sites ( base stations )
2) Switching station ( mobile telephone switching office or MTSO )
3) System operator and its local office
4) Cellular telephones

The heart of the system is made up of individual radio coverage areas called " cells. " Each cell is a self-contained calling area. Within the cell, a cell site is strategically positioned as a base station for receiving, sending and routing the radio signals of cellular phone calls. Because the cellular system is a radio system, no exact boundary can be drawn on a map. In most cases calls can be place and received throughout the service area, except for certain enclosed areas such as underground parking garages. The No Svc ( No Service ) indicator will illuminate on the cellular phone when in one of those areas or is outside of the service area. The cell site’s transmitter is low powered and does not reach much beyond that cell’s boundaries. That makes it possible to reuse channels ( frequencies ) - a given channel can be used at the same time in different cells, as long as the cells do not border one another, without causing signal interference. This is particularly valuable in urban areas where lots of cellular phones are in use at the same time. All cell sites are connected to the Mobile Telephone Switching Office ( MTSO ), which provides connection into the Public Switched Telephone network ( PSTN ) - the local telephone company. The MTSO also provides other central functions, including call processing, traffic management, and transferring calls as a phone moves between cell sites.

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