Comprises in combination: at least one light source; a support plate for the light source, which is at least one; a protective cover that permits the light emitted by the light source to reach the outside; at least one wall which, in combination with the cover, forms a casing to hold the said light source, in which at least the said support plate has a black coloured surface facing the said cover; and in which the position of said light source, which is at least one, in relation to the casing, is such that it emits the light directly to the exterior.