Hughes suggests this circuit in a 1968 documentation. The circuit uses old transistors that can be replaced with equivalents. MOSFET is the critical component of the circuit.
This is the basic full-scale circuit of an LM3914 for voltage measurement or voltage triggering and...
We found this circuit in the October 1992 Radio Electronics magazine. The frequency is given by C1...
Although most common piezoelectric transducers have a reduction in performance at frequencies...