Douglas · May 17, 2018 says:
According to Littlefuse, the inventor of the ATO fuse, the idea that ATO
means OPEN and ATC means CLOSED is a myth. When Littlefuse applied for
patent rights for the fuse name, they could not patent AUTO, which they
wanted to do since the fuse is intended for vehicle use. So they
patented the name ATO for Auto.

Littlefuse's competitors obviously could not use the ATO name, so they
came up with ATC. Whether the myth of ATO=open and ATC=closed came from
those competitors is not clear. However, you will find that ATO is still
a trademark for Littlefuse, and ATC uses can be found with both closed
and open bottoms - which pretty much debunks the myth.


So what is an APR fuse?

https://www.optifuse.com/fuses-auto-blade-reg-apr.php but it doesn't
say! Not even it its glossary or selection guide.

https://media.digikey.com/pdf/Data%2...DFs/APR-UL.pdf
It seems to have something to do with how fast the fuse blows, but the
first link describes the whole category as Fast Acting/Blade Mounting.

I think the graph is bragging that they do blow quickly, not saying that
they are in any way slo-blo.

Or maybe they are saying they blow within a range of time, but then how
is that different from ATC or ATO?