1814 13 June Mr King, a tin-plate worker, was applied to..on the subject of manufacturing a new description of signal lamp.
1902 July 479/2 The apparatus is simply a new glass for the signal-lamp, facing along the same way and throwing a powerful beam of light over the whole length of the arm.
1992 S. Hall 49/2 A small aperture is cut in the back of the signal lamp.