A Survey of Bell System Progress in Electronic Switching

Two Electronic Switching Systems have been developed by Bell Telephone Laboratories for general application in the Bell System; both are now in quantity manufacture by the Western Electric Company. One of these, known as Xo. 1 ESS, is designed for local central offices, and is the commercial successor to the Morris Electronic Central Office. Its system organization is also potentially suitable for tandem and toll applications. The other system, called No. 101 ESS, is designed to provide electronic private branch exchange services in conjunction with existing electromechanical central offices. It brings to the business community modern P B X and Centrexf features which can be provided economically with this new type of system. * Originally written for the German Bundespost and published in their 1964 Y e a r b o o k of Telecommunications, this article has been updated and is published here by permission f o r readers of the B.S.T.J. t T h e principal features of Centrex are direct inward dialing to extensions, identified outward dialing, and certain switchboard attendant features. 937