Some rotary traffic-switching methods

The paper deals with switching methods which have been developed for the purpose of reducing the amount of telephone equipment or improving the efficiency of the telephone plant. The majority of the methods are based on the well known principle that the average efficiency of a switching element of a perfect group improves when the size of the group is increased whilst maintaining the probability of delayed or lost calls constant. Other methods developed aim at decreasing the time required to establish a selection. The various sections of the paper deal with methods based on the grading principle, the principle of full availability, both-way trunking, tandem trunking, and methods of reducing the switching time. These methods are described with the aid of diagrams and an Appendix deals with the calculation of the average hunting time of a group of backward hunting finder switches.