An electrical circuit control of the type having a knob which is turned by an operator to vary a circuit condition is affixed to the face of an electronic image display device and at least a portion of the knob overlays the image display area. This enables display of instantly changeable...http://www.google.de/patents/US5841428?utm_source=gb-gplus-sharePatent US5841428 - Rotary circuit control devices with changeable graphics
