330 On Loaded Lines in Telephonic 'Transmission. 



line is better than the unloaded line for all distances greater 

 than fifteen miles. If the line representing the experimental 

 results is to be parallel to itself, lowered nine miles we have 

 the curve for a line with terminal transformers, and for this 

 case the loading is shown by the experiment to nearly treble 

 the distance over which transmission of a given volume is 

 obtained, and it actually accomplishes more than that, for 

 the quality is improved. The tests upon which this diagram 

 is based were made with telephonic transmission and ear 

 estimates at the other end of the line and are, of course, more 

 or less qualitative, since the difference of quality prevents a 

 sharp estimate. At the transmitting end a person talks in a 

 steady, monotonous manner, and it is arranged so that the 

 person listening at the other end can switch instantly from 

 the loaded line to the artificial cable standard, and vice versa, 

 and alter the length of the cable standard to secure an equal 

 volume of transmission over the two. The comparison gave 

 the equivalents of the two circuits for commercial service, 

 which answered the questions which I had before me. 



For a complete scientific investigation it is desirable to 

 use a sinusoidal current and make qualitative measurements, 

 and we have made some tests in this way. A great deal of 

 experimental work has been done, both upon this cable with 

 the T-14 and other loading coils with different separations 

 between loads, with iron-cored loading coils and with ter- 

 minal transformers, also with other cables and with loaded 

 aerial lines several hundred miles in length, but the results 

 are incomplete, and I am not prepared to attempt a discussion 

 of them at present. 



Any description of the experimental work must include a 

 discussion of the actual performance of loading coils under 

 periodic currents, which is an extended subject. For the 

 mathematical work it has been assumed that the effective 

 inductance and resistance of the coil is the same for all 

 frequencies, which cannot be assumed in experimental 

 work. 



For the extended experimental work which has been 

 done, which has been laborious and most painstaking, I am 

 indebted to Mr. E. H. Colpitis, who has had charge of the 

 experimental tests described above. 



June 7, 1901. 



