Guralp Systems CMG-3TB - Manual (Page 65)

Operator's guide
The signal voltages output by the 3TB are proportional to ground
velocity, and are transmitted from the instrument on balanced
differential lines. In addition, mass position signals are sent as single-
ended circuits referred to analogue ground on the output plug. The
3TB also receives control signals, which are used to clamp and
unclamp the masses, and to run the motors which level and centre the
instrument once in position. Finally, a line is provided for you to apply
a calibrating voltage to the force transducers, thereby measuring the
deflection sensitivity.
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