It is used mainly for long haul links and intercontinental links. Fiber optic cable has the advantages of high capacity immune to interference can go long distances Its disadvantages are, costly difficult to join Cellular Telephone Also known as mobile phones, cellular telephones are a recent technology designed for mobile users who need to make telephone calls from various locations. The telephone is portable and carried with the user. The cellular phone regularly communicates with the nearest cell site to inform the network that it is connected. A Cell Site is a circular geographical area that handles cellular phones within its defined physical space.
Larger coverage is obtained by overlapping cell sites to form a cellular network.
As a user moves location from one cell site to another, the call is transferred to the nearest cell site responsible for that physical area. Each cell site is linked back to a master site that provides an interconnection to the regular telephone network. Calls handled by each cell site are relayed back to the master cell site which then relays it to the telephone network. Frequencies can be reused by other cell sites making for efficient sharing of facilities. Cellular telephone suits large geographical areas, including remote sites.