The present invention relates to a control panel, in particular for a motor vehicle, provided with at least one rotary button (10) for adjusting a parameter relating to an air stream propelled by a ventilating, heating and/or air conditioning apparatus, characterised in that the said adjusting button (10) is an optical encoder with selective light emission and reception, and comprising a rotatable part (20) protruding from the control panel, and a fixed part (30) co-operating with the moving part (20) for emitting and receiving the light. This control panel is adapted to adjust, for example, the temperature, flow rate or distribution of the said air stream.