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Telephone Switching and the Early Bell Laboratories Computers

IP.com Disclosure Number: IPCOM000129381D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Oct-05
Document File: 9 page(s) / 38K

Publishing Venue

Software Patent Institute

Related People



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Copyright ©; 1982 by the American Federation of Information Processing Societies, Inc. Used with permission.

Telephone Switching and the Early Bell Laboratories Computers


(Image Omitted: Note: This article is reprinted from the Bell System Technical Journal, March 1963, pp. 341-353. Copyright 1963, American Telephone and Telegraph Company. Reprinted by permission.)

(Image Omitted: *Superscript numerals designate references at end of article.)

1. Introduction

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 1939 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.

II. The Panel System

Bell Telephone Laboratories and its pre-1925 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 60 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 1903 to 1916, several types of automatic dial systems were developed, built, and soon abandoned. Starting about 1914, however, two successful systems incorporating central control features were developed: the panel machine switching system'* used in the United States and the power-driven rotary system used in several European countries. These systems were probably the first in which the familiar electromechanical relay assumed a dominant role in the design. More specifically, the relay opened new possibilities of automatic control. As a consequence, many of the principles of modern computer design were incorporated into telephone switching at a very early period.

The relay, for example, made possible the efficient conversion from one numbering system to another. This was important because it was realized early that the decimal system of notation was wasteful of equipment in the machine handling of numbers. One of these conversions was incorporated into the relay call indicator, subsequently known as the panel call indicator,2 used in transmitting calle...