I have some lists [1] I use to hide YouTube's constant recommendations of things I've already watched. They also hide previously watched music videos, which may be a downside.

1. https://caleb-vincent.io/post/2025-10-01_youtube-filters/#ju...

Those outlets existed because pre-NEMA there were competing parallel and tandem bladed plugs/sockets [1]. The plugs you saw were probably like examples 2 & 3 in that link. The parallel configuration became NEMA 5-15P and the tandem became NEMA 2-15P.

The NEMA 6 series is wider than the 5 series and the 6-15P probably won't fit in those old outlets, but the NEMA 2-15P would. . . if you could find one.

1. https://plugsocketmuseum.nl/NorthAm2.html

Linux, usually very old and very well tested Linux.

Things that are almost Linux, like LynxOS

Lighter RTOSs like VxWorks.

If it's simple box it may be bare metal.

Oh, and sometimes Windows (but generally not for anything with a safety effect).