M BELL SYSTEM TECHNICAL JOURNAL 



quently transposed and its current ratios practically follow the simple 

 propagation law mentioned above over the frequency range shown. 



Even though a circuit is very frequently transposed, its propagation 

 constant is slightly affected by the presence of other circuits on the line. 

 This may be explained by consideration of Figs. 2B and 7. As previ- 

 ously explained, Fig. 2B indicates the indirect transverse crosstalk by 

 way of a tertiary circuit in one thin transverse slice of a parallel 



5 10 15 20 25 30 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 6 — Effect of transpositions on attenuation of an open-wire pair. 



between two long circuits a and h. The circuit c has currents and 

 charges due to crosstalk from the disturbing circuit a. These currents 

 and charges not only alter the crosstalk currents in circuit h but also 

 react to change the transmission current in circuit a. Since circuits 

 a and c are loosely coupled, this reaction effect could usually be esti- 

 mated with sufficient accuracy by calculating the crosstalk from a to 

 c and back again and neglecting the further reactions of the change 

 in the current in a on the current in c, etc. 



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