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.
The 556 consists of a double integrated circuit 555, which can be replaced by them in this...
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
This circuit is from American documentation from 1970. It can be designed with a BC558 and for the...