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The past decade has seen the worldwide introduction of electronic switching with stored program control. Initially the application of this new technology was in local exchanges but today electronic systems are being introduced into trunk systems as well. One of the latest applications is No. 4 E.S.S., a very large trunk switch. This system, in combination with local systems such as No. 1 E.S.S. and new signalling arrangements, offers major innovations in telecommunication service. The introduction of stored program electronic switching at the local level in the Bell System has led to literally hundreds of new services and features being made available and many more being developed or planned. With stored program control and new signalling arrangements in the connecting trunk systems, the door is opened to both extending the local services and introducing totally new services. These trends are discussed along with examples of possible services. Finally, the effects on development, manufacture, administration, and the customer are reviewed.

The flying spot store is a semipermanent information storage system developed for use in an electronic switching system which utilizes cathode ray tube access to information stored on photographic emulsion. Parallel optical channels are used to provide high capacity and parallel readout. A feedback system provides rapid and precise beam positioning for writing and readout. This paper describes the fundamental design considerations for memory systems of this type, stressing physical realizability, speed, capacity and other system features. The characteristics of a laboratory model are presented.

This paper is an introduction to the No. 1 electronic switching system, a new general-purpose switching system developed for use in the Bell System. Organization and objectives of the system are outlined to provide a background for the detailed technical papers which follow.

Distortion in feedback amplifiers and other non-linear circuits is analyzed for the case where the magnitude and phase of the feedback varies with frequency. The analysis is limited to cases where the distortion products are small compared to the fundamentals and where the non-linear element can be described by a power series having only a few terms. However, many practical amplifiers are adequately described by the analysis. Formulae are derived for a number of third-order products and their dependence upon various feedbacks at second order frequencies is demonstrated.

The equalization and regulation problems of the L3 system are described and a theory of equalization of complex systems is outlined. The location and function of the various equalizers are explained, including the roles and design of the various fixed, dynamic, and manual equalizer networks. The analogue computer used in the regulation system is described, together with the cosine-equalizer adjusting technique used with manual equalizers. Finally the circuits and operation of the regulation system and its components are presented.

The equalization and regulation problems of the L3 system are described and a theory of equalisation of complex systems is outlined. The location and function of the various equalizers are explained including the roles and design of the various fixed, dynamic and manual equalizer networks. The analog computer used in the regulation system is described together with the cosine-equalizer adjusting technique used with manual equalizers. Finally the circuits and operation of the regulation system and its components are presented.

Communication between the various units within no. 1 ESS demands a complex network of transmission lines. The requirements are radically different from previous offices became a large amount of information must be transmitted at high speed, in digital form, between a multiplicity of locations with a high degree of reliability. A description is given of objectives and of organization and operational modes for the network. The problems involved are discussed together with the hardware by which the objectives were successfully realized.

A fully electronic telephone central office is being developed for experimental Bell System service. Both the electronic devices themselves and their system organization represent major changes in the art of telephone switching. The electronic switching system consists of electronic voice frequency switches controlled by electronic memory and logic. However, the system is not designed on the basis of direct substitution of electronic circuits for corresponding relay circuits of an existing switching system. Rather, the electronic circuits are organized in ways that exploit the advantages of the electronic technology.