The MARK L-4C-3D, made by MARK PRODUCTS, is a 3-component geophone. Adaptor cables are available for EarthData recorders.
The connector has been replaced by a self-cleaning type. The wiring also has been changed: Resistors are added internally to obtain a damping of 0.7, and for a standardized calibration of each single component.
Seismometer 170 Units: 3 components, 1 Hz, 5500 Ohms coil resistance
Sensor 3 orthogonal geophones
Sensitivity 180 Vs/m (due to built-in damping)
Response Ground velocity from 1 Hz to >100 Hz
Damping set to 0.7 by built-in resistor
Weight 13 kg (incl. adjusting plate)
Operating Temperatures -20 to + 60 °C