AN IMPROVED TELEPHONE SET 241 



on such problems at all stages. A thorough knowledge of the field needs, a 

 pyramiding technical know-how of physical principles, materials, and struc- 

 tures, and their application in design and in production, and an increasingly 

 comprehensive grasp of measurement technology, guided systematically by 

 correlation with effects on performance in the hands of the public, provides 

 a solid foundation for this confidence. 



By no means the least important factor in this result is that of measure- 

 ment in its broad aspects, conceived and developed as a method of evalua- 

 tion of design in terms of realized performance. 



Methods of Evaluation 



The invention of the vacuum tube gave great impetus to quantitative 

 physical measurement in all phases of the telephone art, as pointed out in 

 W. H. Martin's article in this issue of the Journal.^ Along with this, develop- 

 ment and application of statistical and sampling theory and analysis, and 

 continuing use of the so-called psychophysical test — a big new name for the 

 traditional Bell System habit of remembering the human factor — have pro- 

 vided increasingly powerful tools for laboratory test of new designs. It should 

 be reaHzed that the value of such tests is only in direct proportion to the 

 deliberate effort made to correlate their results, as well as those of the tradi- 

 tional laboratory ''life" test, with effects in actual service. It is, perhaps in 

 this grafting of newer measurement technology on the sturdy and depend- 

 able stock of the "trial installation" that resides the greatest assurance of 

 the significance of the answers. A further assurance that the subscriber gets 

 what he wants is the increasing practice of asking him directly, by means of 

 carefully constructed opinion surveys. 



All of these techniques of evaluation, plus the inevitably intense self 

 criticism which is a matter of course in all Bell System projects, has been 

 applied in the evolution of the new set from the first model to service trial 

 and production. 



General Features 



The illustrations (Figs. 1 & 2) show the new set to be of completely new 

 form, inside and out, low and sweeping in its lines and pleasing to the eye 

 of the great majority of users. On the appearance design, laboratory engi- 

 neers worked with Mr. Henry Dreyfuss, one of the country's leading ex- 

 ponents of functional design. The handset is smaller, and some twenty-five 

 per cent lighter than the existing type. The dial characters are external to 

 the periphery of the fingerwheel where they are more easily seen over wider 

 angles of vision, and are not subject to the inevitable wear of the surface 

 which occurs under the fingerwheel. The cords are jacketed with neoprene, 

 grommeted at the handset end for longer trouble-free life, and are less subject 



