This circuit was found in an Elektor from the 90s. It is a circuit that generates different types of sound effects. The components are still common today.
This circuit that can amplify signals from 0 to 30 MHz was found in a 90s Popular Electronics....
This high voltage circuit was found in a 2005 Linear Technology application manual. The circuit...
This circuit was found in a 1965 Radio Shack documentation. The transistors are from that time....