High Intensity Vapour Arc and Gas Discharge Tubes
There are a number of facts that make discharge lights interesting. Firstly, unlike an ordinary filament lamp the light does not come from a white-hot glowing wire. The light is emitted entirely from the gas atoms excited from conducting electricity. As the gas atoms emit the light as a result of electron transitions within the atom, the light is unique to the type of gas. Atoms in this state are known as ionised which is often referred to as 'Plasma' - the 'fourth state of matter'. The generic neon sign has exploited the unique colours produced by electrical discharge of gases at low pressure.
The pictures on this page link to the category below:
Low and high pressure sodium lamps
Low and high pressure mercury lamps and metal halide
Neon style indicator lamps, Spectral tubes, and neon sign tubes
Special application lamps, super high pressure, deuterium lamps
Carbon filament lamps were replaced with tungsten many years ago. Due to poor efficiency these have also now been phased out. Incandescent lamps produce more heat than light.
There is more information on my larger collection of lamps on the 'lamps' link on the tool bar hosted by Lighting Gallery.