The transient response of seismographs is probably the more important instrumental characteristic of these devices and may be computed analytically subject to some simplifications. Recourse to direct laboratory tests would be a useful procedure for determining this type of response, both as a check on the theory and for the development applications. Many early devices designed to test seismographs dynamically were rather crude affairs and aptly named "shaking tables". However, the prior art discloses with apparently but a single exception no shaking table truly capable of reproducing transient motions other than the natural oscillations of the device itself. The purpose of this paper is to describe the theory and construction of an electromechanical transducer system which does reproduce vertical mechanical motions in the image of arbitrarily specified waveforms for the transient testing of seismographs. Results of such tests on commercial seismometers is included.