This circuit was found in 1980s American documentation. The transducer is a piezoelectric capsule and the power supply voltage can be between 3 and 18 V.
This proximity relay circuit was found in the July 1990 Radio Electronics magazine. The supply...
This circuit is from an old operational amplifiers manual. However, the setting applies to modern...
Using an operational amplifier, the figure shows how to convert the waveform to low frequency...