In 1989, Philips developed the D1 bulb, which was also offered by Osram later on. For an extra charge, the 7-series BMW could be equipped with Xenon gas discharge lamps as a Xenon light from 1991 onwards, for example. Since 1999, the same bulb has been used for the low beam and high beam in the Mercedes-Benz CL Xenon high beam (BI-Xenon). Meanwhile, Xenon headlights with integrated BI-Xenon curve lights have even been introduced as well.
Xenongas produces an enormous light impulse via an electronic ballast shortly after ignition and thus starts up the bulb rapidly, which is important for any automotive bulb - Double Xenon headlights consist of four bulbs and four ballasts. The fourfold service life is also advantageous compared to halogen bulbs which, in order to make their light appear bluish, carry the suffix "Xenon" and have been equipped withan attached color filter or a blue glass bulb.
Xenon bulbs are subject to ECE standardization and are divided into types, such as D1S, D3S, D2S, or D4S Xenon bulbs, for example. The letter "D" stands for "discharge,"while the successive number refers to the respective version. Replacing D1 or D2 Xenon bulbs with D3 or D4 bulbs and vice versa is not advised because another control unit is required. Xenon bulbs offer bright Xenon light, low energy consumption, a long service life, great light density, and efficiency.