A preheat fluorescent lamp "starter" (automatic starting 
switch) is required in bigger tubes which must be struck at 
high voltage in the range of a thousand volts. When 
starting the lamp, a glow discharge will appear over the 
electrodes of the starter. This glow discharge will heat 
the gas in the starter and cause the bi-metallic electrode 
to bend towards the other electrode. When the electrodes 
touch, the two filaments of the fluorescent lamp and the 
ballast will effectively be switched in series to the 
supply voltage. This causes the filaments to glow and emit 
electrons into the gas column by thermionic emission. this 
process is repeated by the starter untill the spontanious 
filament emition.

In order to provide the required voltage for the ionisation 
process