BS 1546:1963

Tungsten filament lamps for use in lighthouse optics and similar beam projection apparatus on d.c. or single-phase a.c. supplies. Operating voltage 100 V but some lamps for operation on 240 V mains supply and some for battery operation at 50 V. Pre-focus caps, lamp rating and reference number, dimensions, filament dimensions and shape, nominal efficiency, nominal voltage, luminance, nominal average life. Selection of lamps, duration of flash, and lamp apparatus under reduced voltage appended.