This circuit is based on a Siemens S566B integrated circuit. The circuit is from a Radio Electronics Experimenter and also has a digital control input.
Using power transistors of the time, this source was published in Radio Electronics magazine in...
Found in an American publication on transistors from the 60's, this circuit uses a transistor...
This circuit is from a very old publication, from the 60s. It uses germanium transistors from the...