Found in an old Elektor, this circuit uses two 7-segment displays to indicate the volume of an amplifier. The circuit uses components that are still common today.
Suggested by General Electric in a 1967 publication, this circuit uses the D13T1, an uncommon SCR...
This circuit is from the 80's component manual itself, but can be applied to more modern...
Suggested by a 1965 Electronic Design, this circuit was originally proposed for oscilloscope...