This 80's circuit uses a microcontroller programmed to generate various songs. The circuit can serve as the basis for a modern design, for example using Arduino. The old circuit included a small audio amplifier.
In the figure we have the way to use the LM3914 as a scale of bar LEDs or moving point. The...
We found this circuit in a European publication of the 1980s. The transistor could be the BC549. The...
We found this simple continuity tester in a 1995 documentation. It uses two LEDs to indicate...