Micro siren (CB21234E)

This circuit with the LM3909 can be powered with voltages from 3 to 5 V. We found it in a Popular Electronics from the 90s.

2 to 9 kHz PLL Synthesizer (CB4566E)
We found this circuit at Modern Electronics in January 1991. The magazine no longer exists, but...
Bidirectional switch (CB9162E)
Found in a 90's EDN, this circuit can be used as a shield. The components depend on the MOSFETs...
Cooking Timer (CB18596E)
This circuit will trigger an audible warning signal after the end of the pre-programmed timing. Using...