No. 4 ESS: The switched digital network plan

A plan for the introduction of time-division switching in the intertoll network is outlined. The plan uses the No. 4 ess as the switching vehicle. The plan defines a Switched Digital Network (sdn) which can evolve compatibly with the existing Switched Analog Network (san). The plan introduces 64 kilobits per second time-division multiplexed pcm as a standard switching signal format in the intertoll network. Facilities utilization, trunk design, timekeeping, and maintenance plans which are required for the new format are presented. Effects on intertoll network evolution, particularly voice performance, are assessed.