This paper clarifies the relation between the diameter k and the edge or node connectivity Ce or c,, of digraphs. The following two inequalities are derived: where n is the number of nodes, d is the maximum degree, and d is the minimum degree.

Microprocessor application to a switching system, especially to telephone terminals, is expected to change switching system architecture. From this viewpoint, Basic Experimental Switching System (BESS) is designed as a functionally distributed control switching system accommodating intelligent terminals. This paper describes BESS hardware and software structures. BESS has the following characteristics. 1) Microprocessor controlled terminals can store and forward dialed digits, and can exchange data between them. Almost all services can be realized merely by a program stored in each terminal itself. 2) Functionally distributed controller of only three untailored microprocessors can treat 100 basic calls. 3) Program flexibility is especially realized by distinct exchange program separation into algorithm, data management and network control parts.