LAYOUT AND THE CONTROL OF INTERFERENCE 



Recording 

 electrodes 



First stage Third stage 



valve holders valve holders 



(a) 



Preparation 



Indifferent 

 electrode 



Additional^ 

 pick-up loop J 



Supplying 

 in -phase. -- 

 F ^signal 



Recording 

 electrodes 



Second stage 

 valve holders 



First stage Third stage 

 valve holders valve holders 



Preparat 



(b) 



Indifferent 

 electrode 



Second stage 

 valve holders 



Figure 42.12 (a) Bad arrangement; (b) good arrangement 



Recording 

 electrode 



Preparation 



(a) 



Indifferent 

 electrode 



Recording 

 electrode 



Preparation 



Indifferent 

 electrode 



(b) 



R«:ording 

 electrode 



Indifferent 

 electrode 



(0 



Figure 42.13 (a) Bad; (b) rather bad; (c) good arrangement 



662 



