Car bulbs are divided into different interfaces according to different lighting needs. According to the function of the light, it can be divided into width lights, turn signals, fog lights, low beams, high beams, reversing lights, license plate lights and daytime running lights.

　　H1, H4 and H7 are three different types of bulbs, they all have halogen and xenon lamps. The H1 terminal is grounded by the bulb shell, the H4 is a double filament for the far and near beams, and the H7 is two terminals. The xenon lamp is divided into a high beam with a lens and a low beam with a lens according to the bulb form.

　　1. H1 (high beam)

　　①.Advantages: The light is concentrated and the brightness is high, which can improve the sight and expand the observation field.

　　②. Disadvantages: The brightness is too strong, causing the driver on the opposite side to be blinded instantly, the perception of speed and distance is decreased, and the judgment of width is decreased; therefore, there is a great safety hazard in using this kind of light.

　　2. H7 (dipped beam)

　　①.Advantages: Wide irradiation range.

　　②. Disadvantages: The irradiation distance is short, but it is not easy to detect dark objects still on the road.

　　3. H4 (far and near light)

　　①.Advantages: Both the low beam and the high beam are in one bulb, which can be used for two purposes.

　　②. Disadvantages: The lamp bowl is too large, and the high beam cannot be concentrated normally. The lights are usually yellow and feel stronger than no lights, but the color temperature is not enough, the brightness is not enough, and the lighting distance is not enough.