ABSTRACT
The complete digitalization of the telephone network at both the transmission and switching levels is an aim pursued by most telecommunication companies worldwide. Maintenance aids based on microcomputers can be easily conceived and inexpensively implemented to lower maintenance costs and improve the quality of service. The microcomputer network is organized in several distinct hierarchical levels. The data in the network is transmitted along leased telephone lines. A high degree of utilization, hostile environmental conditions, and vandalism can cause a low mean time between failures in many coin boxes, which affects the public image of the phone company in a negative way. The local unit is based on a low-power, single-chip microcomputer. The availability of low-cost and reliable microcomputers enables the use of digital techniques to supervise the performance and aid in the maintenance of crossbar telephone exchanges and public telephone coin boxes.
