Found in a 1970s documentation, this mini-organ toy circuit makes use of an integrated circuit from that time. This component is difficult to obtain today.
This transmitter for the 80-meter band (3.5 MHz) was found in an old documentation for radio...
I found this circuit in a 1976 magazine, but it can still be easily assembled, as all components are...
This transistorized circuit with germanium transistors was found in a publication from the 1960s....