A system providing an electrical pulse to mechanically drive a first piezoelectric element upon receipt of an electrical signal from a mechanically driven second piezoelectric element. The system is adapted to provide a preselected frequency of from 16 to 115 impulses per second. The electrical signal from the second piezoelectric element is processed through a voltage comparator by comparison with a reference voltage and applied to a pulse stretcher circuit. The pulse stretcher circuit controls the gate of a silicon controlled rectifier which provides a signal from a power supply to an autotransformer that boosts the voltage from the power supply and applies the voltage to the second piezoelectric element. The pulse stretcher provides the additional function of preventing oscillation in the circuit.