240 THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1951 



the years among the operating, development and manufacturing organiza- 

 tions. 



An important phase of the development of the new telephone set has 

 been the contribution made by the Western Electric Company. Many of 

 the parts for the development models were made by the Western so that 

 the skills or faciUties at the manufacturing plant could be brought to bear 

 on the projects at the earliest possible date. As a result of this activity on 

 Western's part, many changes in design important in large scale manu- 

 facture were introduced in the development stage so that later tooling for 

 production could proceed with directness and assurance. During the course 

 of the development of the various components and assembly of these into a 

 set, joint studies by the Western engineers and the Laboratories were made 

 to bring about a set that would not only meet the basic objectives but 

 that would also be suitable for large scale manufacture at the lowest possible 

 cost. 



From the field, the laboratory, and the factory comes knowledge of service 

 needs, systematic advances in technical knowledge of structures and ma- 

 terials, invention, and production skill. This reservoir of knowledge is ordi- 

 narily tapped deeply to produce a new telephone set which can fully satisfy 

 the severe requirements imposed. The reservoir must be refilled to permit 

 further significant and worthwhile improvement, and can be profitably 

 tapped only as this has occurred. Both these processes were delayed some 

 five years by the war. 



Toward the end of that time comparison of technical possibilities with 

 service needs gave promise of worthwhile accomplishment, with one im- 

 portant proviso: the design would have to be completely integrated and 

 considered as a unit structure. Each component would thus be considered 

 only on its merits in contributing to the overall result. The development was 

 undertaken on this basis and its justification is embodied in the values 

 produced and demonstrated in the 500- type set. This set is new in concept, 

 in execution, and in performance. 



Broadly the new set provides improved technical performance in all 

 functions: transmission, diahng and ringing. It is compatible with existing 

 plant operating conditions, needs fewer codes to provide the same scope of 

 plant and commercial flexibiUty, and, as far as experience so far can deter- 

 mine, in laboratory test and in the field requires less maintenance effort. 

 These performance advantages are accompanied by better appearance and 

 by added general convenience and ease of use to the subscriber. 



These are large claims, and it is only reasonable to ask how they can be 

 substantiated and evaluated at such an early stage of actual experience 

 with the set. The answer can be given with considerable confidence because 

 teamwork, consistently applied, has evolved continually improved attack 



