Found in a Popular Elecronics from the 90s, this circuit appears in other versions in this section and on the website. The circuit draws one of 10 LEDs and has a sound effect produced during the draw.
This circuit was obtained from an old American documentation, and practically any general-purpose transistor...
This transistorized circuit appeared in a Radio Electronics magazine in March 1958. The frequency range...
This old common analog telephone circuit was found in 1967 American documentation. The circuit uses...