Tube lamp

Mercury vapour lamp

Sodium vapour lamp

Neon lamp

bluish light

yellowish light

reddish light

greenish light

400 to 600 V

400 to 550 V

400 to 500 V

400 to 450 V

at a very high pressure

at a high pressure

at a medium pressure

at a low pressure

To limit the power factor

To limit the starting current

To limit the voltage

To limit the energy