What does the 'H' in car lights mean?

[ElliotLynn]

Car light 'H' indicates the filament form and socket type of the lamp. Here are specific explanations about car lights: 1. Models: Different models cannot be mixed. H1 is a single-filament, single-pin type, mostly used for high beams, and sometimes for fog lights. H7 is a single-filament, double-pin type, mostly used for low beams, and sometimes for fog lights. H4 is a dual-filament, three-pin bulb where both low and high beams are in one bulb, with standard wattages of 55W for low beam and 60W for high beam. 2. Lighting etiquette: When two cars meet head-on, a short 'beep' is a form of greeting. This 'beep' is light and brief, not causing annoyance to the other party. It is generally used for drivers greeting each other or drivers greeting pedestrians, and is also a polite expression when passing each other.