238 BELL SYSTEM TECHNICAL JOURNAL 



In the case of a single tertiary circuit, the electric and magnetic 

 effects expressed by the interaction coefficient are simply related and 

 the interaction coefficient is simply related to Fi. With many tertiary 

 circuits the relation between the electric and magnetic fields of any 

 one tertiary circuit is altered by the presence of the others and the 

 relative importance of electric and magnetic fields in the interaction 

 effect varies among the tertiary circuits (except for the ideal case of 

 " non-dissipative " circuits). In a practical case, therefore, the inter- 

 action coefficient is only approximately proportional to F,. Measure- 

 ments of the interaction coefificients by indirect methods have, however, 

 indicated that the approximation is satisfactory for purposes of 

 practical transposition design. 



