30Hz to 100Hz vertical and horizontal geophone. CDJ middle & high frequency geophones, 4,10,15,28,30,40,60,80 or 100Hz, are widely used to seismic prospecting of petroleum, coal, metallurgy, national defense, engineering and etc.SPECIFICATIONS CDJ-Z/P30CDJ-Z/P38CDJ-Z/P40CDJ-Z/P60CDJ-Z/P100 Vertical/HorizontalVertil/HoriVerti/HoriVerti/HoriVerti/HoriNature Frequency Fn (Hz)30±5%38±5%40±5%60±5%100± ...