| http://www.w3.org/ns/prov#value | - A hinged lens ring 28 is secured to the front face of the housing 20 in any suitable manner, as for example by screws indicated as 29 The lens ring is very close to the vertical plane VV through the light center so that the housing limits" the spread of light which can escape from it to substantially a hemisphere with the center of the hemisphere at the light source LC'.
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