278 3Ir. W. Dudclell on Hoio to Improve Telephony. pMarch 16, 



Mr. A. Blondel, and the Engineer-in-Chief of the Post Office, 

 Mr. Gavey,* have published many results obtained in this way. 



A more complete insight into the distortion produced by different 

 parts of the apparatus and line can be obtained by gearing small 

 mirrors to both the transmitter and receiver diaphragms, so that 

 records can be obtained simultaneously of the movement of the trans- 

 mitter diaphragm, the current flowing into the line or cable, the 

 current flowing out of the line, and the movement of the receiver 

 diaphragm. [With the above apparatus the effects produced by resist- 

 ance, capacity, and self-induction, both separately and in combination, 

 and also distributed, in the form of an artificial cable, were demon- 

 strated at the discourse.] 



There still remains much work to be done in devising new 

 methods of measurement, and in improving the present apparatus : 

 nevertheless the existing methods and apparatus are already suffi- 

 ciently perfect to enable a large number of investigations to be 

 successfully undertaken. 



If the necessarily brief references to the complex problems of 

 telephony and the resume of the methods of measurement available 

 to attack them which I have given to-night should inspire any of 

 our engineers or scientists to undertake systematic quantitative 

 measurements with a view to improving the transmission of sounds 

 and speech, then this discourse will have accomplished its aim, and, I 

 think, justified its title — " How to Improve Telephony." 



[W. D.] 



* Journ. Inst. Elec. Eng., xxxvi., p. 32, 1905. 



