o carry many of these services and devices of this kind and would make it easier and cheaper to provide non telephone services to rural and remote areas.Subscriber terminals are normally connected to local exchanges by a physical pair of conductors. The physical conductors are expensive, representing around 30% of the total capital cost of plant in urban areas. However, in highly populated areas, a suitable local network distribution system can be planned and installed that can be expanded economically. Local networks use overhead or buried cables in various size and flexibility points, allowing sufficient capacity to accommodate new subscriber. Various means of concentrating traffic are available so that more than one subscriber may share each physical pair of conductors.However, local distribution represents the major problem of providing telephone service in rural and remote areas. In rural areas, subscribers may be at a distance over 30 to 50 kilometers from the exchange and the terrain and environment communication transfer even more difficult. Local network cost may represent as much as 70 to 80% of capital plant cost which are themselves normally 4 to 5 times of urban cost.An alternative to physical conductors, especially in rural areas, is radio telephony. Ultra High Frequency and Super High Frequency systems have direct line of sight paths between transmitter and receiver at a distance of 50 to 70 kilometers. In practice the environment and terrain reduce this distance, Improving the utilization of frequency spectrum is possible by using the cellular radio concept and other methods of dynamic frequency assignment.Manual systems with operators setting up connections using key plugs and jacks are still used in developing countries. If attended for 24 hours a day, these provide reasonable service with low investment, low consumption of power and simple maintenance.In automatic analog systems, speech is converted into a e...
