Found in a 1980s documentation, this circuit uses as base a component of the era. The formula for determining the conversion is given next to the diagram.
This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and...
This circuit uses matched transistors. The circuit is from Electronics Now magazine and has a...
This tone-modulated transmitter produces a tone with frequency depending on C4 and C5. Free...