An LED module (200) comprising: a first set of LEDs (D1) for emitting illumination to illuminate an environment, arranged within a first circuit path; a second set of one or more LEDs (D2) for emitting light, arranged within a second circuit path; both the first and second sets being powered by a portion of the power received via a same pair of input terminals, and the first circuit path being longer than the second circuit path; and filter circuitry (206, 208) arranged to filter a modulation in the power received via the terminals, the filtering comprising allowing a component of the modulation at a predetermined modulation frequency to be passed only to the second set of LEDs (D2) and not the first set (D1), thereby causing a corresponding signal to be embedded in the light emitted by the second set but not in the illumination emitted by the first set.