Polarity of GDTs (Gas Discharge Tubes)

We’ve gotten a few questions on how to find the polarity for GDTs, AKA gas discharge tube arresters. However, this turns out to be a moot point as these parts are not polarized, which means they have no “negative” or “positive” side.

One thing that causes confusion is that schematics will show a dot inside the symbol for the GDT, which can be interpreted as showing polarity. However, this is not the case, the dot simply denotes that it is a gas-filled device.

Example of Schematic Symbols

For more general information about GDTs and other circuit protection devices, have a look at the following post:
Differences in Circuit Protection Devices

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