On Oct 19, 2013, at 10:13 AM, Liam Proven <lproven at gmail.com> wrote: Interesting. http://www.cs.virginia.edu/about/images/mus_024.jpg says that this is "similar to power tubes used on the early computers". I very much doubt that. The tube in question looks like an Eimac 4-125A (if so, it would be a tetrode). That tube is used in transmitters, in the driver or final amplifier stage when several hundred watts are required. I can think of no place in a computer that would use this, except perhaps a large CRT display with electrostatic deflection. The CDC 6000 console (DD60) is the only beast of that kind I know, and it uses a similar tube but smaller and very different in construction, the 3CX100A5. If this were Wikipedia, that entry would earn a {{citation required}}. paul