A control for use upon a solid panel, devoid of control shaft apertures, allows data entry by rotational positioning of an electrode to vary the capacitance to at least one of a multiplicity of electrodes formed upon an interior surface of the panel. A magnetizable disk is attached to the exterior of the panel, with the control knob having a magnetized member attracted to the disk for maintaining the control knob in proper position while allowing control knob rotational adjustments. A light-emitting display is positioned behind the panel to indicate the index of the control knob by means of a variable-length, circular bar of light.