A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand.

Thesis (M.Eng.) - Asian Institute of Technology, 1973

This thesis begins with a brief account of the outside plant in a telephone system, and an outline of planning methods. Part of the outside plant consists of underground cables enclosed in pipes. In the Telephone Organization of Thailand demand forecasts are made for twenty years ahead. Pipes are laid every twenty years and cables are laid every ten years to meet this demand. It is the purpose of the study in the present thesis to determine the most economical program for laying pipes and cables in phases. The method developed has been applied to one section of a new distribution network planned for the Nakorn Pathom area. The cost of the chosen section of the network has been calculated for a range of different time intervals between pipe-laying and cable-laying operations. The results show that it should be most economical to lay the pipes every twenty years and to lay the cables every four or five years. A second more general model involving costs of replacing old cables and pipes, and allowing for costs varying with time is proposed. Finally, the interaction between telephone works and other public utility works in a city is briefly discussed.