This variable frequency oscillator with the 4093 was found in a Popular Electronics from the 90s. The table gives the component values for various frequency ranges.
This circuit was found in a 1977 documentation. With it we have the direct indication, through LEDs...
Found in American documentation from the 1990s, this circuit causes the fuse to blow in the event...
This 1989 documentation circuit uses a digital display with components that are uncommon today,...