System Testing of the No.1 Electronic Switching System

and software and for evaluating over1 electronic switching system are detest facilities and the early results the first two No. 1 ESS installations Planning for system testing started at the beginning of the No. 1 electronic switching system (ESS) development. 1 Test facilities were designed concurrently with the design of the system. This paper describes the test plan being followed, the test facilities that are being used and the results t h a t were obtained on the first two No. 1 ESS installations. The first No. 1 ESS, located at the Holmdel Laboratories, is being used for checking system design. The second No. 1 ESS at Succasunna, N. J., is the first of a large number of systems scheduled for commercial service. Fig. 1 broadly illustrates three sequential periods of testing. Factory tests are followed by system tests and, after cutover of an office to service, by maintenance tests.-' Fig. 1 also depicts system evaluation, an activity which has its beginnings in the planning and design stages and carries through many issues of a new system. Factory testing is a subject on which there are many views. Most views include some degree of device and package testing, and inspection for w o r k m a n s h i p -- s u c h as the quality of the wired connections. Beyond that they range from continuity checks of mounting plate assemblies and major units to functional tests of groups of major units or subsystems, and on out to rather complete system testing. The major units of the Holmdel system, after very little factory testing, were shipped directly to Bell Laboratories for extensive design testing prior to use in the 2575