364 BELL SYSTEM TECHNICAL JOURNAL 



and phantom loading apparatus, and in other apparatus associated with 

 phantom circuits and their side circuits. 



The New York-Denver Line 



This project was especially significant in utilizing the recent radical 

 advances in the telephone transmission art to achieve a specific long distance 

 objective which constituted a recognized necessary preparatory step in a 

 broad fundamental plan for transcontinental telephony. 



This line made use of the phantom circuit of loaded 165 mil open-wire 

 phantom groups installed between New York and Chicago (via Buffalo) 

 and between Omaha and Denver, during 1910. The intermediate Omaha- 

 Denver portion of the circuit initially consisted of a 165 mil non-phantom 

 pair loaded with the new side circuit type coils. Some time later, a second 

 165 mil pair on the line was moved to pins adjacent to the first mentioned 

 pair so that these two pairs could be phantomed and the phantom loaded. 

 From then on, the New York-Denver circuit was a continuous phantom 

 circuit. The new high-efficiency type of phantom-deriving repeating coil 

 was used throughout this installation. 



The construction work on the initial layout of the line was completed in 

 December 1910, and the first through talk was made on December 29, 

 1910. (These are the reasons for describing this project as a 1910 develop- 

 ment.) Commercial service, however, did not start until May 8, 1911. 

 The intervening time was utilized in clearing up noise and crosstalk trouble 

 which the time schedule and the lack of complete engineering information 

 had made it impossible for the engineers to predetermine and take care of 

 in advance. The initial transmission tests showed the side circuits to be 

 satisfactory with respect to transmission and noise. The phantom, how- 

 ever, was very noisy and the phantom-to-side crosstalk was quite heavy. 

 The line crosstalk difficulties were found to be mainly due to transposition 

 irregularities, including omitted transpositions. For noise reduction, con- 

 siderable retransposition work was necessary in regions where inductive 

 interference prevailed and some rerouting in entrance cable portions in- 

 volving the use of selected pairs in existing non-quadded cables. 



When the line was opened for public use, the transmission performance 

 was as good as had been expected when the project was planned. Cross- 

 talk and noise were well within tolerable limits. The theoretical equivalent 

 was about 28.5 db (appreciably better than the equivalent of the older non- 

 loaded 165 mil circuits between New York and Chicago). According to 

 the standards for long distance transmission that were worked to in the 

 period under discussion, the transmission was considered to be satisfactory 

 between terminal stations in New York and Denver, but the margin of 

 transmission was not great enough to provide really satisfactory service 



