Abstract: Control, comprising a knob (12a) with a prism (20) that has an axial part (22) located centrally in the knob, with a symbol display surface (28) at an external end (30) of the knob, and a part (24) arranged at an angle to the central part for receiving incident light from a symbol illuminated by a light source (34), which symbol is on a stationary disc element (32) located at an end of the knob (12a) facing away from the external end (30) and concentric with this, in order to be able to display different symbols by optical projection towards the symbol display surface (28) depending upon the rotational position of the knob (12a).