250 THE BELL SYSTEM TEC3miCAL JOURNAL, APRIL 1951 



and closed. These data indicated that for a satisfactory minimum audibility 

 of the ringing signal at positions where the ringer should be heard, over the 

 range of conditions encountered in service, a louder ringing signal than that 

 of the present station ringer would be desirable. A lower pitched signal 

 was also indicated as carrying better, particularly for that considerable 

 portion of the population whose hearing has deteriorated with age. 



It was also known, however, that any such increase in ringing level, if 

 not adjustable at will, would increase the all-too-frequent requests for the 

 telephone man to come and adjust the sound to suit the subscriber's needs 

 at the moment. 



The new ringer, by combination of magnetic design skill with mechanical 

 ingenuity, has succeeded in apparently meeting all these requirements 

 most satisfactorily to all concerned. It is lower pitched, and more efficient 

 as well as more effective. The easy volume adjustment provided the sub- 

 scriber has in fact nearly eliminated his requests for such readjustment by 

 the maintenance man. In view of the lower pitch of the signal, and the mini- 

 mum level which can be set by the subscriber, the manual adjustment feature 

 apparently has not increased the number of cases where the bell cannot be 

 heard. 



The ringer electro-magnetic design provides a structure which is more 

 efficient and higher in impedance than previous designs. This permits ade- 

 quate loop range with greater numbers of connected extension or party line 

 stations. The higher impedance at audio frequencies combined with a re- 

 duction in low frequency receiver response limits the inductive susceptive- 

 ness of the set to as low values as with previous sets having 5 db less re- 

 ceiving sensitivity. 



The foregoing description of general objectives, methods and results 

 provides some background for more detailed consideration of the design of 

 the components of the set and of the contributions of the Western Electric 

 Company manufacturing department in working out with the development 

 engineers practical methods and designs for efficient quantity production. 



Each of the components of the set as well as the over-all assembly has 

 novel and valuable features contributing to the final results. It is these 

 significant features, rather than the complete design of each component, 

 which are discussed in the following paragraphs. 



Component Design 

 Handset 



As already pointed out the handset. Fig. 9, is of a radically new form, 

 smaller, lighter and easier to use than previous types. As in the case of its 

 predecessor, it is made of phenol plastic, a molded-in cavity through the 

 handle serving as a conduit for the separate leads to the receiver. Contact 



