Essential Considerations Relating to Modern Telephone Network Plans

Abstract

During the last ten years, considerable attention has been given to all aspects of telephone network engineering. A large amount of research work has helped to define precisely the factors that affect the intelligibility of speech conveyed over telephone networks. There has also been a clear and marked development in greater exploitation of existing resources and provision of new media to provide blocks of circuits at low costs. The problem of arranging groups of circuits to provide the fastest service with the greatest economy over large areas has been more clearly understood.

On these developments, the most important one is that leading to provision of blocks of extremely reliable circuits over long distances at extremely low costs. At present, methods have been devised and more methods are being evolved to increase the number of circuits that can be provided on open-wire pairs, symmetrical cable pairs, coaxial tubes, microwave radio relay links, etc. The standardization of a few types of equipment and incorporation of signalling facilities have greatly reduced the costs of carrier terminal and repeater equipment. The introduction of transistors is also likely in future to play an important part. In addition new media like the use of special plastic insulated cables, small tube coaxial cables, waveguides, etc., hold still further prospects of lowering the costs provided proper planning of the network is undertaken.

Thus, at present it is possible to provide blocks of extremely reliable long-distance circuits at a small fraction of the cost that obtained a few years ago. This has paved the way to providing a fully automatic telephone service wherein a subscriber in any part of a country can dial any other in that country, and such a service has been or is being introduced in all modern countries. The ultimate aim of all administrations including the Indian P. & T. is to provide such a service and in the meantime to proceed towards a rapid manual service. The introduction of such a rapid telephone service should include consideration of the engineering, traffic, economic and switching aspects.

The subject of the paper is to give briefly important points on each one of these aspects and show how these are taken into account while planning a national telephone network.