The Development of a Handset for Telephone Stations* 



By W, C. JONES and A. H. INGLIS 



A number of factors contribute to the dititiculties involved in the design 

 of a telephone handset which gives as good service performance as a desk- 

 stand. The handset transmitter, for example, not only is used in a wider 

 range of positions but also is moved much more frequently, so that wider 

 variations are experienced in its characteristics. 



Further difficulties are introduced by the close physical connection 

 of the receiver and transmitter, in that "howling" tends to be set up. 



The handset has been developed so that it overcomes all these difficulties 

 and is interchangeable with the deskstand in existing telephone plant without 

 important reaction on either transmission or signaling performance. 



MANY interesting development problems are presented in the 

 design for general use of a handset which provides the conven- 

 ience of this arrangement of a telephone set without a sacrifice in the 

 performance of the system. It is the object of this paper to discuss 

 some of these problems and to describe their solution as embodied in 

 the handset now being furnished by the Bell System. 



The idea of mounting a telephone transmitter and receiver on a com- 

 mon handle to form a handset was conceived early in the development 

 of the telephone. In 1878, only a few years after the invention of the 

 telephone, handsets of the type shown in Fig. 1 were in use by operators 

 in the Gold and Stock exchange in New York City.^ Variable resist- 

 ance transmitters of the Edison type were used in these handsets. 

 This transmitter employed a relatively insensitive lamp black resist- 

 ance element which was soon superseded by the more sensitive granular 

 carbon type in order to permit the extension of telephone service to 

 greater distances. The basic ideas underlying the variable resistance 

 transmitter and the many advantages of granular carbon over the 

 numerous other materials which have been tried have been discussed 

 elsewhere.^ It is sufficient to point out here that the large amplifica- 

 tion afforded at low cost by a well designed granular carbon transmitter 

 makes it unlikely that any other structure will offer successful compe- 

 tition in general telephone application for some time to come. 



When an attempt was made to use granular carbon transmitters 

 with handsets it soon became evident that a satisfactory design in- 



* Presented at A. I. E. E. Midwinter Convention, Jan. 25-29, 1932, New York, 

 N. Y. 



^ "Beginnings of Telephony," F. L. Rhodes, Harper and Brother, 1st Edition, p. 

 153. 



2 "The Development of the Microphone," H. A. Frederick, Journal oj the Acousti- 

 cal Society of America, July 1931, Part 2, p. 17; Bell Telephone Quarterly, July 1931. 



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