NEU'IR.IUZATION Ol- lELEGRAl'Il CROSSE I RE 



425 



indicate the disturbing current, the feathered arrows the crossfire 

 current and the dotted arrows the neutrahzing current. The last 

 mentioned current is inijiressed upon tlie (hsturhed circuit X l)y 

 means of a transformer connection (T) between the " apex " or trans- 

 mitter branches of the two circuits. It will be obvious that if a 

 good duplex balance has been obtained the neutralizing impulse 

 will divide practically equally between the real and artificial lines 

 of circuit X and substantially none of it will pass through the receiv- 

 ing polar relay of circuit X, on account of the balanced bridge ar- 

 rangement. It will therefore have no effect on signals received at 



Station A 



Loaded Phantom Grouo 

 Wire! 



Fig. 6 — -Effect of loading coils on crossfire 

 Note: -^ Signalling Current •"*" Induced Current 



A, but will generate neutralizing impulses which will travel over X 

 to B so as to appear at B at the same time as the crossfire currents. 

 It has been found possible to employ coupling such that the receivang- 

 end crossfire is practically eliminated in the polar relay. The proper 

 poling of the neutralizing transformer has been found to be as indicated 

 in Fig. 5 for all types of circuit to which the device has been applied. 

 The crossfire impulse has the direction shown, for the reason that 

 capacity coupling predominates. 



Line Characteristics 



The first part of this section will be devoted to a discussion of 

 the effect of loading and line transpositions. This will show why, 

 in the telephone plant, it is necessary to deal with crossfire among 



