The invention relates to an illumination device connectable to an AC voltage source for applying an alternating voltage during a series of time intervals. The illumination device comprises at least a first light source and a second light source, arranged to be connected in series to the AC voltage source, to generate a luminance output in response to the alternating voltage. Selection means are provided configured for selectively applying the alternating voltage over the first light source or the first and second light source. A controller is provided for controlling the selection means in response to a data signal comprising data symbols such that one or more of the data symbols are contained in said luminance output. The invention also relates to a method of embedding one or more data symbols in the luminance output of such an illumination device, an optical receiver and an illumination system.