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Oldcodger · 22nd Apr 2019, 9:58 pm

Bit of history .
Another side to #9- for years railways ran signal head lamps ( dual filament 12v ,can't remember the wattage) below 12. Something like 11.5v for the main and a bit less for the reserve. This was because longevity was the requirement. I remember seeing something about Halogen replacements, where the voltage had to 12 . Then LED ones came in ,the reason being much improved life.

22nd Apr 2019, 9:58 pm	#17
Oldcodger Nonode Join Date: Oct 2014 Location: West Midlands, UK. Posts: 2,181	Re: The lightbulb conspiracy Bit of history . Another side to #9- for years railways ran signal head lamps ( dual filament 12v ,can't remember the wattage) below 12. Something like 11.5v for the main and a bit less for the reserve. This was because longevity was the requirement. I remember seeing something about Halogen replacements, where the voltage had to 12 . Then LED ones came in ,the reason being much improved life.