Concentric

Concentric switches have a double shaft system. You can have two separate switch functions within one switch. Choose concentric knobs which fit to the shafts of the concentric switches which often is 6mm or 1/4" and for the inner shaft 1/8". Concentric functions can be found on vintage studio gear like Neve consoles where you can select the frequency with the outer ring and the boost/ attenuation with the inner knob part.