The impulse of high voltage (alternating current about 25 000 V) from the control unit of a gas-discharge headlight moves between conclusions of its lamp, initiating the gas category in xenon which filled a lamp.

At xenon excitement temperature in a lamp of a gas-discharge headlight rises, evaporating mercury, and there is an electric arch.

Mercury and electric arch cause the further growth of temperature in a lamp, iodide evaporates and decays, atoms of metal give the saved-up energy, producing light.

Fig. 7.16. Design of a gas-discharge headlight: 1 – In +; 2 – control unit of a gas-discharge headlight; 3 – conclusion; 4 – lamp of a gas-discharge headlight; 5 – gas xenon; 6 – metal atoms; 7 – iodide; 8 – mercury; 9 – light