Found in a 90s documentation, this circuit appears in other configurations on this site. The circuit can be powered with voltages from 5 to 12 V.
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...