The tags associated with a voltage are back. SE discourages the deletion (burnination) of tags. The problem with these tags is they don't really define a group of questions well (a 5V tag could describe many many different types of circuits).
Delete the 24V, 12V, (and maybe 5V, 3.3V) tags and discontinue use of tags associated with a voltage
These had been cleaned up before, and they are back. There are probably a few hundred of these. I propose we create a new power-rail tag and merge them with that.
The other option is we could delete them, if we cleaned them and had a really good reason for deletion.