This circuit has a sensitivity of 2uW. We found it in documentation from the 1980s. The integrated circuit is from that time. Equivalents can be tried.
Found in a 1965 Radio Shack documentation this oscillator can be used with modern general purpose...
In the figure we have a voltage / frequency converter circuit that can be used as a transducer interface...
This small stereo amplifier for headphones was found in a documentation on integrated circuits from...