Found in a Motorola documentation from the 70s, this circuit makes use of transistors of the time. Modern equivalents can be used. The diode also supports an equivalent.
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...