Editing Headlamp (section)

=== Mechanics ===
==== Acetylene Gas headlamp ====
{{Main|Carbide lamp|Gas lighting}}
The earliest headlamps, fuelled by combustible gas such as [[acetylene]] [[gas]] or oil, operated from the late 1880s. [[Carbide lamp|Acetylene gas lamps]] were popular in 1900s because the flame is resistant to wind and rain. Thick concave mirrors combined with magnifying lenses projected the '''acetylene flame light'''.<ref>{{cite web | url=https://knowhow.napaonline.com/fire-automotive-lighting-history/ | title=On Fire: Automotive Lighting History » NAPA Know How Blog | date=27 January 2015 }}</ref> A number of car manufacturers offered [[POL valve|Prest-O-Lite]] ''calcium carbide acetylene gas generator cylinder'' with gas feed pipes for lights as standard equipment for 1904 cars.

==== Electric headlamp ====

The first electric headlamps were introduced in 1898 on the [[Columbia Automobile Company|Columbia Electric Car]] from the Electric Vehicle Company of Hartford, [[Connecticut]], and were optional. Two factors limited the widespread use of electric headlamps: the short life of filaments in the harsh automotive environment, and the difficulty of producing dynamos small enough, yet powerful enough to produce sufficient current.<ref>{{cite book |last= Georgano |first= G. N. |author-link= G.N. Georgano |title= Cars: Early and Vintage, 1886-1930 (A World of Wheels Series) |year= 2002 |publisher= Mason Crest |isbn= 978-1-59084-491-5 |url-access= registration |url= https://archive.org/details/worldofwheels0000unse }}</ref>

[[Peerless Motor Company|Peerless]] made electric headlamps standard in 1908. A Birmingham, England firm called Pockley Automobile Electric Lighting Syndicate marketed the world's first electric car-lights as a complete set in 1908, which consisted of headlamps, sidelamps, and tail lights that were powered by an eight-volt battery.<ref>{{cite book|last= Walker |first= Richard |title= The Eventful Century |year= 1999 |publisher= Reader's Digest |isbn= 978-0-276-42259-1}}</ref>

In 1912 [[Cadillac (automobile)|Cadillac]] integrated their vehicle's [[Delco Electronics|Delco]] electrical ignition and lighting system, forming the modern vehicle electrical system.

The Guide Lamp Company introduced "dipping" (low-beam) headlamps in 1915, but the 1917 Cadillac system allowed the light to be dipped using a lever inside the car rather than requiring the driver to stop and get out. The 1924 Bilux bulb was the first modern unit, having the light for both low (dipped) and high (main) beams of a headlamp emitting from a single bulb. A similar design was introduced in 1925 by Guide Lamp called the "Duplo". In 1927 the foot-operated dimmer switch or dip switch was introduced and became standard for much of the century. 1933–1934 Packards featured tri-beam headlamps, the bulbs having three filaments. From highest to lowest, the beams were called "country passing", "country driving" and "city driving". The 1934 Nash also used a three-beam system, although in this case with bulbs of the conventional two-filament type, and the intermediate beam combined low beam on the driver's side with high beam on the passenger's side, so as to maximise the view of the roadside while minimizing glare toward oncoming traffic. The last vehicles with a foot-operated dimmer switch were the 1991 [[Ford F-Series]] and E-Series [Econoline] vans.{{Citation needed|date= July 2010}} [[Fog lamp]]s were new for 1938 Cadillacs,{{Citation needed|date= July 2010}} and their 1952 "Autronic Eye" system automated the selection of high and low beams.

Directional lighting, using a switch and electromagnetically shifted reflector to illuminate the curbside only, was introduced in the rare, one-year-only 1935 [[Tatra T77|Tatra]]. Steering-linked lighting was featured on the 1947 Tucker Torpedo's center-mounted headlight and was later popularized by the [[Citroën DS]]. This made it possible to turn the light in the direction of travel when the steering wheel turned.

The standardized {{convert|7|in|mm|0|adj=on}} round [[sealed beam|sealed-beam]] headlamp, one per side, was required for all vehicles sold in the [[United States]] from 1940, virtually freezing usable lighting technology in place until the 1970s for Americans.<ref name="HeadlampHist">{{cite web|url= http://deepblue.lib.umich.edu/bitstream/handle/2027.42/49367/UMTRI-98-21.pdf&embedded=true?sequence=1 |title=Headlamp History and Harmonization |first=David W. |last=Moore |work=The University of Michigan Transportation Research Institute |date=June 1998 |access-date=21 March 2021}}</ref> In 1957 the law changed to allow smaller {{convert|5.75|in|mm|0|adj= on}} round sealed beams, two per side of the vehicle, and in 1974 [[rectangular]] sealed beams were permitted as well.<ref name="HeadlampHist"/>
[[File:Mercedes-Benz, Techno-Classica 2018, Essen (IMG 9795).jpg|thumb|Two Mercedes-Benz SL: right with US-spec sealed beam type headlamps; left with normal headlamps for other markets]]
Britain, Australia, and some other [[Commonwealth of Nations|Commonwealth]] countries, as well as Japan and [[Sweden]], also made extensive use of 7-inch sealed beams, though they were not mandated as they were in the United States.<ref name="motivemag">{{cite web |url=http://www.motivemag.com/pub/feature/tech/Motive_Tech_The_Difference_Between_US_and_European_Lights.shtml |title=Prometheus, Bound: The differences Between American and European Lighting |access-date= 2010-12-29 |archive-url=https://web.archive.org/web/20090501102913/http://www.motivemag.com/pub/feature/tech/Motive_Tech_The_Difference_Between_US_and_European_Lights.shtml |url-status=dead |archive-date= 1 May 2009}}</ref> This headlamp format was not widely accepted in continental Europe, which found replaceable bulbs and variations in the size and shape of headlamps useful in car design.

Technology moved forward in the rest of the world.<ref name="HeadlampHist"/><ref name="motivemag"/> In 1962 a European consortium of bulb- and headlamp-makers introduced the first [[halogen lamp]] for vehicle headlamp use, the [[H1 Lamp|H1]]. Shortly thereafter headlamps using the new light source were introduced in Europe. These were effectively prohibited in the US, where standard-size [[sealed beam]] headlamps were mandatory and intensity regulations were low. US lawmakers faced pressure to act, due both to lighting effectiveness and to vehicle aerodynamics/fuel savings.<ref name="motivemag"/> High-beam peak intensity, capped at 140,000 candela per side of the car in Europe,<ref name="R48"/><ref name="Rumar41">{{cite report |title=Relative Merits of the U.S. and ECE High-Beam Maximum Intensities and of Two- and Four-Headlamp Systems |date=November 2000 |last=Rumar |first=Kåre |url=http://deepblue.lib.umich.edu/bitstream/handle/2027.42/49438/UMTRI-2000-41.pdf |access-date=2014-12-13 |publisher=University of Michigan Transportation Research Institute}}</ref> was limited in the United States to 37,500 candela on each side of the car until 1978, when the limit was raised to 75,000.<ref name="Ehrhardt"/><ref name="HHH"/> An increase in high-beam intensity to take advantage of the higher allowance could not be achieved without a move to halogen technology,<ref name="Ehrhardt">{{cite tech report |title=Halogen Sealed Beam Headlamps |year=1979 |last=Ehrhardt |first=Ralph A. |publisher=SAE International |doi=10.4271/790200}}</ref> and so sealed-[[Light beam|beam]] headlamps with internal halogen lamps became available for use on 1979 models in the United States.<ref name="Ehrhardt"/><ref name="HHH">{{cite journal |title= Headlamp History and Harmonization |journal= Motor Vehicle Lighting |date= June 1998 |last= Moore |first= David W. |url= http://deepblue.lib.umich.edu/bitstream/handle/2027.42/49367/UMTRI-98-21.pdf |access-date= 2014-12-13}}</ref>
{{As of |2010}} [[halogen]] sealed beams dominate the sealed-beam market, which has declined steeply since replaceable-[[bulb]] headlamps were permitted in 1983.<ref name="motivemag"/>

[[High-intensity discharge lamp|High-intensity discharge]] (HID) systems appeared in the early 1990s, first in the [[BMW E32|BMW 7 Series]].<ref name="100Hella"/><ref name="Litronic"/> 1996's [[Lincoln Mark VIII]] was an early American effort at HIDs, and was the only car with [[direct current|DC]] HIDs.