3-decade VCO (CB21326E)

This circuit generates signals from 10 Hz to 10 kHz. We found it in a Popular Electronics from the 90's. The components admit equivalents.

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Single Pulse Generator 555 (CB13280E)
The MC15555 of this circuit is the old version of the common 555. What this circuit does is...
Sophisticated Alarm (CB4865E)
We find this circuit in an American 1980s documentation. The circuit can still be assembled...
Light alarm (CB22056E)
This circuit triggers an LM380 oscillator, producing an audio tone with light falling on the LDR....