Chap. 10] 



ELECTRICAL METHODS 



775 



hai 



Outpu t 



Nemhdicattr 



UoflflflJ 

 00"000 ' 



Output 



Fig. 10-97. Buzzers for electromagnetic prospecting. 



^h 



^ # 



% — I Output 



^iiipU 



Ikctifitr 



Oscillator 

 (»bov0 



Fig. 10-98. Vacuum tube oscillator and power amplifier for electromagnetic methods 



(adapted from Miiller). 



