No.1 ESS Switching Network Plan

This article presents the topology, traffic properties and control of the switching network for No. 1 ESS. Companion articles describe the physical implementation of the network1 and its control.2 In the near future, an article dealing with the program control will be published. To assist the reader with unfamiliar terms, a brief list of definitions is given in the Appendix. In connection with the plans to develop an electronic central office, the problem of switching network design has received much attention. Due to the many, often conflicting, requirements and possible choices of technology and geometry, the synthesis process requires a fair measure of that ill-defined catalyst commonly referred to as "intuition." The invention and the successful development of the ferreed3-4 provided the technological solution that resolved the early difficulties of all-electronic networks. The ferreeds provide a metallic transmission path while retaining high switching speed. Among the early recognized requirements was the desire to use the switching network not only for the obvious function of interconnecting lines and trunks, but also for all link functions -- connections between signal transmitters and trunks, ringing circuits and lines, etc. The reasons behind this requirement were to simplify trunk circuits, to eliminate the problem of engineering and administering several different networks, to simplify control, to provide the connecting function at high efficiency and to provide full freedom to associate trunks with all types of signaling circuits.