This invention relates to an illumination system (100) comprising a plurality of luminaires (101a-d). The luminaires are each arranged to transmit in the light emitted an identification code ID. To ensure sufficient detection of the identification codes during selection with a selection device (120), the system further comprises a control unit (130) which is arranged for identification of any luminaire which has a nominal drive value equal to or below a minimum preset value, or equal to or above a maximum preset value. The control unit sets (or instructs a driver to set) the nominal drive value of such identified luminaire to a predetermined value to achieve a corresponding predetermined light output from the luminaire ensuring a sufficient signal for the transmission of the identification code ID.