Glossary
Amber lamp
A term for yellow flashing lamps. The Y in lamp designations like PY21W stands for yellow.
Asymmetrical light distribution
The low beam illuminates more of the kerb side of the road than of the oncoming carriageway. Standard since 1956. See also Z characteristic
Base
Carries the burner and makes the electrical connection. Its precision is important for exact orientation of the light beam.
Bilux
Actually a trademark of OSRAM for two-filament lamps. Commonly used as the designation for the old R2 headlight lamp without halogen technology.
Burner
Part of an incandescent lamp, comprising the coiled filament and the bulb made of hard or quartz glass.
Candela
Abbreviation: cd. Unit of measure for brightness. Latin for a candle, which emits roughly 1 cd light.
D…
Designation for gas discharge (xenon) lamps. Examples: D1, D2R, D2L, D3, D4. The D stands for discharge.
DOT
Department of Transport. Approval granted in the USA, equivalent to ECE. Many lamps nowadays have both approvals.
DRL
Daylight running lights.
E mark
Approval mark. The number after the E indicates the country in which approval was granted, e.g. E1 = Germany, E2 = France.
ECE
Economic Commission for Europe. A UN agency based in Geneva. Harmonizes construction regulations for motor vehicles. Binding in numerous countries, also outside Europe.
Festoon lamp
Tubular lamp with contacts at the ends. Customary for interior and licence plate lighting.
Filament
The filament of an incandescent lamp is designed not just as a simple wire, but as a coil. It is even doubly coiled in the Truckstar lamps from OSRAM for 24 V, meaning that a coil is doubled up on itself.
Gas discharge lamp
See Xenon light
H…(number)
Halogen. E.g. H7 = halogen automotive lamp.
H4
Most common two-filament lamp for low and high beam.
H7
Common one-filament lamp for low and high beam; very high luminous efficiency.
Halogen
In lighting engineering, the designation for lamps with a glass bulb in which a cyclic process takes place. Tungsten evaporated from the glowing filament settles on it again. The name comes from the chemical composition of the gas with which the lamp is filled. A vacuum is present in non-halogen lamps.
HB…(number)
Originally a US lamp; nowadays, also often approved in Europe. Examples include HB3 and HB4. Not to be confused with H3 and H4.
Hg
Chemical symbol for mercury (Latin: hydrargyrum). Type D1 and D2 xenon lamps still contain roughly one-third of the quantity of this heavy metal that can be found in a domestic energy-saving lamp. Xenon lamps based on the newer D3 and D4 types are totally mercury-free.
HID
High-intensity discharge = Xenon light
KBA
Kraftfahrt-Bundesamt; the German authority responsible for issuing approvals according to the ECE rules.
Kelvin
Abbreviation: K. In lighting engineering, the unit of measure for the color temperature. Incandescent lamps are in the region of 3,200 K, xenon light in the region of 4,000 K. Daylight has roughly 7,500 K. LEDs can be set within a wide range. The smaller the number, the warmer the effect of the light.
LED
Light-emitting diode.
Light/dark boundary
On low beam and fog lights, only very little light may be present above this line in order to avoid glare.
Longlife
Lamps bearing this mark last up to three times longer than standard versions. Example: Ultra Life from OSRAM.
Lumen
Unit of measure for the luminous flux, i.e. for the total quantity of light generated. Abbreviation: lm
Luminance
The density of the light.
Luminous flux
The total quantity of light generated. See also Lumen
Luminous intensity
The luminous intensity quantifies the portion of the luminous flux (see below) which is emitted by a light source in one direction and – very importantly! – is also perceived by the human eye. This is why every infra-red lamp has a luminous intensity of zero, no matter how much luminous flux it generates. For infra-red light is invisible to the human eye. Luminous intensity is measured in candelas (cd). A household candle has around 1 cd.
Lux
Abbreviation: lx. Unit of measure for the luminous intensity, i.e. the light that gets onto the road, for example.
On-board voltage
When the car engine is running, this value is between 13 and 14 volts. Headlight lamps are optimized for the range from 13.2 to 13.8 volts. The battery voltage of 12 volts only applies when the engine is off. The on-board voltage of commercial vehicles is 28 volts.
Pb
Chemical symbol for lead (Latin: plumbum). All lamps from OSRAM are lead-free and thus bear a crossed-out Pb.
R2
Obsolete R2 two-filament headlight lamp for low and high beam. Now only found in very old vehicles. See also Bilux
Reference number
Comes after the E number on high-beam lamps and gives a rough indication of the output. The sum of all high-beam lamps on a car may not exceed 100.
Tungsten
The material of which the filament is made.
Tungsten filament
The filament of a lamp.
UV-cut
The lamp emits no UV light. All automotive lamps from OSRAM are of this kind.
Wedge
A lamp with a glass base produced by squeezing ("wedging"). Example: W5W for parking lights, side blinkers and instrument lighting.
Xenon
Actually a noble gas, but often used as a synonym for gas-discharge headlights.
Xenon light
Headlight with gas discharge lamps.
Z characteristic
A light distribution optimized for xenon light that looks like an inverted Z on the wall.
15-degree rise
Part of the asymmetrical low beam. Part of the light rises to the right at an angle of 15 degrees.