160 



BELL SYSTEM TECHNICAL JOURNAL 



the ends of the disturbed pair is measured, the far-end or near-end 

 crosstalk values are obtained readily. In fact, the magnitude of the 

 near-end crosstalk is given by the expression 



N\ = 



Vn 



E 



(58) 



and the magnitude of the far-end crosstalk is given by the expression 



F\ = 



Vr 



E e- 



(59) 



Taking 20 logm j^ and 20 logio-j-pr, we obtain an equivalent loss in 



db between the disturbing and disturbed levels of the two crosstalking 

 circuits. This consideration determined the method of measurements 

 used in our experimental studies. 



Fig. 4 — Crosstalk measuring circuit arranged for far-end measurements. 



The circuit used is given in Fig. 4. The two branches of the meas- 

 uring set are the comparison circuits, the upper containing the cross- 

 talking system and the lower including adjustable attenuators. The 

 input and output impedances of both branches are kept alike by 

 adjusting the resistances Ri and i?2- Thus, when the lower branch of 

 the circuit is adjusted to produce the same input into the detector as 

 through the crosstalking branch the loss in the calibrating branch gives 

 an equivalent crosstalk loss in db. These values of crosstalk in db 

 below the input level in the disturbing circuit are plotted on all our 

 sketches. 



