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.
This circuit reproduces the dial noise in a small speaker. The transistor can be a general-purpose type....
We found this circuit in an 80's schematic. The circuit uses LEDs in series with zeners to...
This circuit turns off after a time given by capacitor C1. This component can have from 1 to 1,000...