Abstract: An impact printer is described which includes a shock wave generator means, a print hammer, and a solid wave guide interposed between the shock wave generator and print hammer. The solid wave guide acts to transmit a shock wave from the shock wave generator to the print hammer to cause its movement towards a substrate upon which printing is to occur. In a preferred embodiment, the shock wave generator comprises a piezoelectric or electrostrictive actuator, which actuator is held in compression by a frame that prevents any substantial longitudinal movement thereof. In a further preferred embodiment, circuitry is connected to the actuator for detecting, after an actuation, the return of the hammer into contact with the solid wave guide. In response to that detection, the circuitry provides a signal which enables operation of the shock wave generator.