On Permutation Switching Networks

Two-sided communication switching networks with an equal number of input and output terminals (N) have been looked upon as permutation generators of order N.1'2 Alteration of the permutation being produced by any state of the network configuration may be achieved by rearranging or changing the state of the switching network. By limiting the switches in each stage to binary action devices certain economies have been achieved. 3 This paper describes additional savings, particularly in the number of required operating elements. Some further savings are achieved by introducing break contacts into switching networks. II. T H E /? E L E M E N T A small space division switching network is a two-by-two array of crosspoints (see Fig. 1). Each of these crosspoints is generally considered as either electromechanical make-contacts or electronic twostate devices. Confining our attention to make-contacts, they may be actuated by a coordinate mechanism, as in a crossbar switch, or as individual relays. Usually in switching networks the crosspoints are controlled so that only one may be operated in any column and row. Such use of 2 x 2 arrays confine the maximum number of states from the 16 possible states to those useful in switching networks. The 16 states 813