The document introduces a supplemental light-signaling devices concept for multiple lamp systems. A master lamp meeting all requirements may be accompanied by one or more supplemental devices without photometric requirements for the supplemental devices. An IM reference number limits the sum of all devices mounted on a vehicle to below 100. Supplemental devices require separate marking. Color, switching, failure, and installation requirements apply to all devices of a function together. The approach permits combining devices from different manufacturers with individual type approvals.