148 



BELL SYSTEM TECHNICAL JOURNAL 



Because of other requirements which a balancing coil must satisfy, 

 the winding arrangement actually employed is shown in Fig. 5. The 

 simple device of Fig. 4 is not balanced from the standpoint of longi- 

 tudinal crosstalk for any coil setting except that of zero mutual induc- 



Fig. 6 — Trial balancing coil construction. Container is 432" in length and 1/^" in 



diameter. 



tance. The Fig. 5 arrangement is such that theoretically there is no 

 magnetic coupling between the two circuits for longitudinal currents in 

 either one, regardless of the coil setting. Unless the capacitance be- 

 tween primary and secondary windings can be kept very small, the 

 resultant admittance unbalance produces crosstalk which is not com- 



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