Abstract: 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 calibration marks and/or other graphics in close proximity to the circuit control including at locations immediately adjacent to the perimeter of the knob. Electronic components of the control are contained within the knob and a base member at the front of the panel. Components of this kind may be embedded in or attached to the knob itself enabling easy repair by simply replacing the knob and/or may be contained in an easily replaced carrier that fits within the base. Knob motion sensors include radio frequency sensors, capacitive sensors, Hall effect sensors and photoelectric sensors among others and enable the controls to be compact, durable and enable economic manufacture.