capacitorsymbol [~]
Trying to repair an old Hameg CRT oscilloscope and looking at the schematics for the HV Z board I see the following capacitor symbol (in red box):
The capacitor itself looks (vaguely) like this:
I'm not suggesting it is a vacuum dielectric cap, it just looks like this. It's about 2 or 3 cm long with a glass tube and two metal ends.
The symbol is different from that used for electrolytics and other non-polarized capacitors (like polys and ceramics).
The dot is not standard. It is a marker on the resistor symbol to indicate pin 1. The only reason I can think of when this is useful is when using the circuit for spice simulations so that you know what side to probe for pin 1 or the orientation for current.
Update: Asked around some more and found someone who does this on schematics! The answer they gave me as to why: "it helps when debugging the board". They place the dot on the printed circuit board as well as in the schematic. That way when they are debugging they can quickly determine which side of the resistor they are probing without having to trace the line.
Avoid this style. You will confuse people!
If I'm looking at the correct symbol, that's a feed through capacitor.
They are common on RF devices where they allow wires to enter a shielded enclosure.
Looking at the picture from the link you gave here they are:
Best Answer
It's the symbol of a gas discharge neon lamp. More info here and Here