This sound meter or sonometer was found in a Popular Electronics from the 80's. The circuit can be easily implemented today, and the microphone is made of electret or ceramic.
This CMOS Flasher was found in a Popular Electronics from 1978. It can still be easily assembled, as all...
This circuit was found in an old manual of linear integrated circuits of the 80's. Equivalent...
With this circuit you can control up to 3 A of LEDs in different sequences, using a PWM...