The application of feedback to an electromechanical transducer, or oscillating platform, designed for the testing of seismographs is described. Accruing advantages are the complete masking of the resonance peak in the transducer velocity response, and immunity of the platform motion to variations in mechanical loading by the seismographs undergoing test.

The superiority of the feedback technique is shown by direct comparison with the operation of the transducer electrically damped by a short-circuited ring.

The transducer constant-velocity output is easily converted to constant amplitude or constant acceleration by means of simple coupling networks.

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