IND UCTI VE COORDINA TION 



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However, for selective signaling purposes party-line stations frequently 

 have the ringer connected, in effect, between one of the line conductors 

 and ground. The unbalance of the party-line station equipment is 

 therefore affected by the impedance of the ringer and its point of 

 connection in the station equipment. The relative susceptiveness of 

 several types of station sets to noise-frequency induction is shown in 

 Table D. 



Table D shows that, with advance planning in areas where noise 

 induction is or may likely become a matter of importance, much can be 

 accomplished by the use of station sets of decreased inductive sus- 

 ceptiveness. Where such types of apparatus are substituted in 

 existing plant, except in gradual replacements or in connection with 

 general rearrangement programs, the expense is, naturally, increased. 



Inductive Coupling 

 As stated above, the inductive coupling between exchange telephone 

 plant and power distribution circuits in urban areas is largely con- 

 trolled by such factors as the street layouts and the joint use of poles. 



(See following page) 



