Crossbar Toll Switching System

Abstract

IN AUGUST of 1943 a new mechanical toll switching system was placed in service in Philadelphia. It was designed by engineers of the Bell Telephone Laboratories and of the department of operation and engineering of the American Telephone and Telegraph Company for large toll centers, particularly those where most of the offices are of the panel and crossbar types. The Philadelphia installation was planned before the war. Even then it was apparent that a mechanical switching system was needed urgently to secure faster and more economical switching. War conditions produced an abnormal growth in toll traffic that accentuated the need for the new equipment. The system was therefore installed as rapidly as the heavy load of war work on the engineering and manufacturing organizations of the Bell System would permit. It is now contributing materially to the war effort by providing adequate switching facilities for the increased volume of traffic.