DEVELOPMENT OF A HANDSET FOR TELEPHONE STATIONS 263 



center of the receiver cap and the clearance between the handset handle 

 and the cheek. 



The data obtained are shown graphically on Fig. 11 together with 

 an outline of the handset drawn to the same scale. All except about 

 3 per cent of the persons shown on the chart can use the handset by 

 holding the receiver to the ear in a normal manner. The others can be 

 accommodated by a slight shift of the receiver on the ear. The effect 

 of such a shift on received speech, for a small number of persons, is 

 unimportant in comparison with the large improvement in transmitting 

 performance for the great majority which results from the decrease in 

 the average distance of the mouthpiece from the lips. 



Performance in Service 



Since the initial introduction of the handset, close contact has been 

 maintained with its performance by tests and observations under ac- 

 tual service conditions, and by the examination of instruments returned 

 from service. 



It has been shown by these observations that, although the output 

 of the handset transmitter as used by the subscriber is on the average 

 lower than that of deskstand transmitters of the most efficient types, 

 the improved response and articulation are an adequate compensation 

 for the lower level. The transmission performance of the handset as 

 rated by the repetitions,'^ has been found to be as good as that ob- 

 tained with the deskstand. 



Undesirable variations in transmission and resistance with change 

 in position, excessive carbon noise, and howling, all of which have here- 

 tofore presented serious obstacles to the adoption of a handset for 

 general use, have been successfully overcome in the design which has 

 been described. It has been found practicable to use this handset in- 

 terchangeably with the deskstand in the existing telephone plant, 

 without important reactions on either transmission or signalling 

 performance. 



That the design, in addition, meets the desires of the public for the 

 convenience of a hand telephone set is best evidenced by the steady 

 increase in demand to more than one million a year at the present time. 



' "Rating the Transmission Performance of Telephone Circuits," W. H. Martin, 

 Bell System Technical Journal, Jan. 1931, pp. 116-131. 



