Indicator tubes for transistor logic machines.

Sign. Terminology changes over time, particularly in technology. When I was young, I learned about "condensers" and "aerials" from my father. "Breadboarding" a circuit meant pretty much that-- constructing it on a plank of wood, preferably using #14 bare copper wire laid out in neat right angles. By the time I was a teenager, my speech habits had been corrected to say "capacitor" and "antenna". I like the distinction between "filament" and "heater". The latter implies that something is being heated. The former implies a standalone glowing wire. "Indirectly heated" and "directly heated" may be a bit more accurate, but the terms are also cumbrous. And whoever heard of "nanofarads" or "picofarads" anyway? ;) Cheers, Chuck