228 BELL SYSTEM TECHNICAL JOURNAL 



CO = lirf where / is the frequency in cycles per second. This current 

 divides equally between the two ends of circuit h. The near-end 

 current is: 



1 Ve 



te 



2 1 _^Z, 



jwCbdx 2 



The near-end direct crosstalk coefficient due to the electric field of 

 circuit a may be called Ne and is the limiting value of the following 

 expression as dx approaches zero : 



la ' Kdx 2KIa " 1 , ^6 , ' 



y-^ +-Ydx 



where K is the frequency in kilocycles. The near-end direct crosstalk 

 coefficient for the electric field is, therefore: 



K\) IMc 2i^/„ 2K ' Ca' 



Ca 



The far-end current due to Ve of Fig. 31 is — ie and, therefore, 

 the far-end coefficient due to the electric field is — TV^. 



The near-end and far-end crosstalk currents of Fig. 31 due to the 

 magnetic field are alike and are designated im which may be calculated 

 as follows: 



. _ Vrn^ _ _ IgjcoMabdx 

 '"^ ~ 2Z, ~ 2Z, 



The near-end or far-end crosstalk coefficients for the magnetic 

 field may be called Nm and Fm. They are alike and equal to the limit 

 of: 



in. 10« , , 



-^ • v^-v- as ax approaches zero. 

 la Kdx 



Therefore : 



_ _ joiMai _ jirMal, 



In the above, Mah is the mutual inductance per unit length between 

 circuits a and h. It is calculated in the same manner as p^h used in 

 computing V e- These methods of computing V e and F„, from the 

 distances rn, ru, Sn, etc., of Fig. 32 are not precise but are sufficiently 

 accurate for open-wire circuits since the diameters of the wires are 



