360 



BELL SYSTEM TECHNICAL JOURNAL 



Figure 1 shows both the new handset and the deskstand forms of 

 mounting, including all these features as integral parts of their design. 

 The new desk type transmitter and receiver can, of course, be used 

 with wall sets. 



The schematic drawing of Fig. 2 indicates the general arrangement 

 of parts in the new station transmission circuit for either type of set. 



(So — 



ANTI-SIDETONE 

 INDUCTION COIL 



TO LOOP 



vOiKLr- 



^ 



¥=^ 



TALK 



■SWITCH-HOOK'^ 



Fig. 2 — Schematic transmission circuit of anti-sidetone coil. 



In describing the results produced by these transmission features, 

 and the methods employed in measuring and rating these results, it 

 seems desirable to include some discussion of the characteristics of a 

 telephone conversation as distinguished from a direct, face-to-face 

 conversation, so that the various effects of the new circuits and 

 instruments may be seen in as correct relative proportion and as 

 generally comprehensible form as possible. 



Some Elements of the Station Transmission Problem 



In either a telephone or a direct conversation, successful cummuni- 

 cation depends on the characteristics of the talker and of the listener, 

 and their reactions to each other and to the character of their sur- 

 roundings. In a direct conversation such, for example, as across a 

 desk, the environment is in general the same for both talker and 

 listener, and their ears are materially aided by their eyes. In a 

 telephone conversation, however, not only may the surroundings of 

 talker and listener be entirely different, but a third element, the 

 telephone system, is added to the environment of each user, which 

 complicates his reaction, not only to his own surroundings, but also 

 to the other party to the conversation. Furthermore, for obvious 

 economic reasons, the natural binaural reception of direct conversa- 

 tion, with its advantages in discriminating between sounds from dif- 

 ferent directions, is replaced in the telephone conversation by a 

 monaural medium. 



