838 



EXPLORATION GEOPHYSICS 



Fig. 519. — 24-trace seismic recording equipment illustrating 

 three amplifiers in unit construction. (A) 24-trace recording cam- 

 era; (B) master control and communication panel; (C) three 

 channel amplifier and filter unit; (D) communication speaker. 

 (Courtesy of Engineering Laboratories, Incorporated.) 



Fig. 520. — A complete set of portable seismic equipment for the recording of twelve 

 traces. (A) amplifiers; (15) camera; (C) control and test panel. (Courtesy of Century 

 Geophysical Corporation.) 



