inner space of the reflector 28 so that the actual light generating element 30 of the light bulb 18 is located inside the reflector 28 the dome shaped reflector 28 is fitted in the region of its large opening disposed in the main direction of illumination with an outwardly facing peripheral collar 32 which lies flat on a ring shaped region of the transparent plate 26 a fixing plate 34 lies on the surface of the collar 32 facing the inner space of the housing 10 and its outer contour corresponds to the outer contour of the transparent plate 26 which is however provided with a central circular cut out for the reflector 28 so that u2014 with the exception of the collar 32 u2014 the reflector 28 can be pushed through this cut out the collar 32 of the reflector 28 thus comes to lie between the transparent plate 26 and the inner marginal region of the fixing plate 34 the fixing plate 34 is in turn now again fixed in its position by four projections 36 which are each located on the inner side of the frame 22 a respective projection 36 is provided centrally at each inner frame side in this connection the projections 36 are provided at their side remote from the collar 24 of the frame 22 with a slope facilitating the introduction of the fixing plate 34 into the frame 22 it can be seen from fig1 that the transparent plate 26 and the fixing plate 34 is so to say clamped and.