On the basis of ECE-R37 or R99 specifications, the lamps shall bear on their base various codes and particulars:
- The name of the manufacturer
- The intended operating voltage based on Regulation 37 is shown as 6, 12 or 24 V (the unit may also be absent).
- H1, H4, H7, P21, W represents the power category e. g. 55 W.
- E1 represents the country of manufacture and approval e. g. "1" corresponds to Germany.
- DOT means that the lamp is also compatible for the US market.
- U corresponds to UV lamps used in bodies with plastic covers.
It is worth noting that when changing a bulb you should not grab it by the crystal as there is a chance that the fingerprints will burn and leave spots reducing the brightness. Also, if a Xenon element breaks indoors, ventilation is required due to harmful gases (except for D3 and D4 which do not contain lead).
Types of lamps
Single incandescent lamp
It is the simplest type of bulb with the lowest efficiency and longest life. It consists of an extremely thin metal element (usually tungsten) which emits light when an electrical voltage is applied to its ends. Because the element is worn away by heat, the higher the wattage of an incandescent lamp, the shorter its life.
Halogen lamps
They represent the evolution of simple incandescent lamps. They are ideal because of their simplicity, cost and lifetime which is about twice as long as that of ordinary lamps (about 500-700 h of continuous operation). They are also called iodine-chalazia lamps because there is inert gas and iodine or bromine vapour inside them (the filament is also made of tungsten).
Xenon lamps
You will also find them under the name HID (High Intensity Discharge). They have much better characteristics than halogen bulbs and are therefore more expensive. The operating principle of high discharge lamps is based on the well-known "photovoltaic" arc (electric discharge). Specifically, the system consists of a high voltage circuit (up to 23 kV) where the special lamps contain xenon gas (Xenon). The discharge and current transfer between the tungsten pins produces light in the ionized xenon environment.
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