Fluorescent lamp starter close-up detail.

A quick close up of a fluorescent lamp starter in action. When voltage is first applied to the lamp a glow discharge takes place in the starter switch that causes the bi-metallic contacts to heat up and close. This connects the filaments at each end of the lamp in series and heats them up to the correct emission temperature for lamp operation. When the starter switch closes, the glow discharge stops and the contacts begin to cool down and after a brief period the switch opens, breaking the circuit. This causes the magnetic field inside the ballast coil to collapse and induces a high voltage pulse across the lamp enabling the arc to strike. The process will repeat until the lamp has started.