More intriguingly, the light bulb is of the incandescent variety — the same type that many consumers now revile for its short life span.
Halogens, a type of incandescent that delivers light the way Edison intended, with a tungsten filament, are now available in the standard bulb shape.
HEIs were said to produce about 30 lm/W with the ultimate goal of doubling that amount.The halogen lamp is a type of incandescent that operates hotter and lasts longer, but its efficiency gains are minimal.
There are enough, however, that the subway still purchases at least 50 different types of incandescent bulbs.
The US government phased out production of certain types of incandescent bulbs as as the country began switching over to more efficient lighting like halogen incandescents, compact fluorescents, and LEDs.
The illumination system is made up of the light source, usually an incandescent lightbulb but sometimes another type of bulb such as fluorescent or halogen, plus an optical system for directing the light efficiently to the film.
Under new legislation, "there are efficiency standards that lamps need to meet," so some types of traditional incandescent bulbs are disappearing, he said.
The decision by EU governments to phase out all incandescent lightbulbs and low-efficiency types of halogen bulbs by 2012 was confirmed on March 18 , 2009
Matt Prescott, founder of Ban The Bulb energy efficiency campaign, said: "Ban The Bulb welcomes the combined efforts of the government, energy companies and retailers to phase out many types of domestic incandescent light bulb, but is disappointed that the measures announced by Hilary Benn are purely voluntary and illustrative".
