This advertisement is from 1965. The text of the ad is reprinted below:

CENTRAL CONTROL SECTION that handles logic and command functions for ESS is shown in background. Foreground shows basic components.

LARGEST SINGLE PROJECT IN BELL SYSTEM HISTORY...

the Bell System's new Electronic Switching System

Succasunna, N.J., has first commercial installation of new switching system that processes telephone calls with modern electronics.

The Electronic Switching System is a new development of Bell Telephone Laboratories and the outcome of a deliberate effort to bring the latest electronic technology to the service of Bell System customers.

More than 2000 man-years were required for its research, development and manufacturing design. Eventually it will be the Bell System’s standard telephone central office.

ESS is designed to switch calls with traditional Bell System dependability—better, faster and, in time, cheaper than ever before.

Its most important feature is a central "stored program" control that directs not only general switching operations bus also specific arrangements for each number served. Special optional services can include the ability to reach frequently called numbers by dialing only three or four digits… dial a third party into a telephone conversation in progress… switch incoming calls to a friend’s home for the evening.

In Succasunna, these optional services are on trial with 200 selected customers. Other ESS's are now being planned and installed in other cities by Western Electric Co, manufacturing and supply arm of the Bell System.

The capacity of ESS to remember and do special things will make your telephone service still more valuable and personal.

Bell System
American Telephone and Telegraph
and Associated Companies

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