Telephone Switching and the Early Bell Laboratories Computers

Various papers, some of them listed in the references, have presented material on two interrelated subjects: (1) automatic data processing as applied to machine switching in the Bell System, and (2) work on digital computation as it grew out of telephone technology and as it was applied to seven relay-type digital computers designed and built at Bell Telephone Laboratories between 1039 and 1950. Together, these papers tell an important story of Bell System contributions to the field of automatic digital computation. It has been felt for some time, however, that a single account of the pertinent facts and developments would be of interest and value. Thus, this paper makes no claims of presenting new material; rather, it is an attempt to bring together many diverse accomplishments and to show their relationships so that a single paper will be available for convenient reference. I I . THE PANEL SYSTEM Bell Telephone Laboratories and its pre-1025 predecessors, the Western Electric Engineering Department and various American Telephone and Telegraph Company groups, have been engaged with problems of automatic data processing for almost GO years. The basic reason, of course, is that any automatic telephone switching system must process digital data, beginning with the signals and dialed digits originated by a customer in placing a call. In the period from about 1003 to 1016, several types of automatic dial 341