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BELL SYSTEM TECHNICAL JOURNAL 



disturbing: circuit and it is necessary, therefore, to transpose both 

 circuits at points B and D. The addition of these four transpositions 

 does not afifect the cancellation of far-end crosstalk in length AC 

 against that in length CE by means of the transposition at C. After 

 the four transpositions are added, length AC is still similar to length 

 CE and the far-end crosstalk currents at E, due to these two lengths, 

 are equal. Therefore, they will cancel when one of them is reversed 

 in phase by the transposition at C. 



It may be concluded that, while transposing both circuits at the 

 same points has no effect on transverse crosstalk, it has a large effect 

 on the interaction crosstalk. An experimental illustration is given in 

 Fig. 10. This figure shows frequency plotted against output-to-output 



X T X T X 



REGULAR TRANSPOSITION POLE; 



TXT 

 ■■ EXTRA TRANSPOSITION POLE 



5 10 15 20 25 30 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 10 — Effect on far-end crosstalk of e.xtra transpositions in both circuits. 



far-end crosstalk between the two side circuits of a phantom group on 

 a 140-mile length of line. The curve marked A is for the two circuits 

 transposed for voice-frequency operation. Curve B is for the two 

 circuits transposed in the same manner except that four transpositions 



