This circuit is from documentation from 1965. However, it can be created with modern transistors. Power comes from two 9 V batteries.
This circuit is from a 1992 publication. The transistors can be the BC549 or BC548 and the power...
This receiver for frequencies up to 18 MHz was found in American documentation from the 1990s. Data...
This toy musical instrument has the notes given by the capacitors on the keyboard. The circuit can be...