Nixie tubes and some early flat panel monochrome screens both use similar technology. They rely on gases being excited into a plasma state by high voltage and emitting visible light. Later 'plasma' colour TV screens use a similar discharge to produce ultra-violet light that then excites coloured phosphurs (red/green/blue) to produce coloured pixels.

Nixie tubes have electrodes shaped into symbols (eg '1','2', '3') or multiple segments (like numeric LED displays). Flat panel plasma displays have a matrix of cells that can be caused to discharge individually, and have electronics to drive columns of cells in a wave or scan across the panel, a bit like refreshing a CRT tube.

On the sidebar there is a list of plasma displays that I have recovered from various pieces of scrap equipment and the linked pages include pinouts etc.

• http://www.desmith.net/NMdS/Electronics/NixiePSU.html Nixie HV Switching PSU

If any referenced page no longer exists, try looking for its URL on http://archive.org.