Abstract: In this mounting system, the bulb (10; 10') may be selected from a first type (10) and a second type (10'). The bulb defines a radial reference surface (11; 11') situated at a predetermined distance d.sub.1 or d.sub.2 from the midpoint (M) of its filament (12; 12'), where d.sub.1 is not equal to d.sub.2. The system comprises a bulb carrier (30) fixed to the reflector and defining a radial thrust surface (32) situated at a predetermined distance (f) from the focus (F) of the reflector; a first adaptor (40) suitable for co-operating with a bulb of the first type; and a second adapter (50) suitable for co-operating with a lamp of the second type. Thus, regardless of the type of bulb mounted on the bulb-carrier by the corresponding adaptor and regardless of the possible type of bulb support, the bulb filament is centered on the axis of the lamp and the axial position of the filament relative to the focus of the reflector is the same.