No. 1 ESS Call Processing

As mentioned in the description of systems objectives' for the No. 1 electronic switching system (ESS), the problem posed to the designer of a switching system intended for the widest possible Bell System use becomes: to provide economical means for switching a wide range of traffic, composed of many types of calls, each differing in some degree from the next. Previous solutions to this problem resulted in systems composed of a multiplicity of switches and relay circuits, each performing a certain set of functions. A call was processed by the proper set of circuits at the proper time. In the more modern systems, common control circuitry takes over the most complicated parts of the decision-making process. For example, the No. 5 crossbar system, as presently developed, is so versatile t h a t it is able to offer a wide range of services. In t h e No. 1 ESS t h e principle of the common control has been carried even further by the use of a stored program electronic data processor, which consists of a central control and associated electronic memories. Relay circuits, such as t r u n k and service circuits, are kept as simple as possible. 2 M a n y of the functions performed by the circuits in previous systems are performed by the central control under the direction of the stored program. T h e logical organization of the central control was designed to take advantage of the speed inherent in electronics for processing large num2483