This astable multivibrator was obtained from a Mullard documentation from 1960. The components depend on the used transistor and on the frequency, as shown in the table next to the diagram.
We found this circuit at Modern Electronics in January 1991. The magazine no longer exists, but...
Found in a 90's EDN, this circuit can be used as a shield. The components depend on the MOSFETs...
This circuit will trigger an audible warning signal after the end of the pre-programmed timing. Using...