The SM-6, made by SENSOR Nederland, is a vertical geophone in a PE-5 case, and with a 75 mm steel spike. The geophone string consists of six geophones spacing 10 metres each, with a lead-in of two metres, and terminated with a PE-7 multiple string connector with wide and narrow clips. Signal Output Generator Constant 28.8 Vs/m (single geophone) Output Signal 27.5 Vs/m (single geophone) Response Ground velocity from 4.5 Hz to > 150 Hz Damping 0.71 (4.5 Hz type)