Our house has had its electrical system upgraded with every generation of technology since it came in to homes, including examples of new outlets wired to older wiring, so you can’t trust it just because it has three prongs. Take this example, where cloth wiring goes into an outlet I don’t recognize, then goes out through metal conduit, an ultimately to new wiring and a nice, new outlet. Don’t trust the outlet.
The entire upstairs has knob and tube wiring, which is always good for some costly drama on the home repair shows. The technology is simple, knobs hold the wire against the joists, like this part going through our attic:
And tubes run it through drilled holes in the joists:
In the end, it shows up in my office as a single two-pronged outlet. This is how it looked when I pulled the outlet from the wall to start replacing it:
Fortunately, one new circuit has already been run to the attic through what was once a closet in the living room. I was able to run wiring from there over to the office and down through the wall, so I have a real outlet in the office now. The ethernet cable I had to string along the hot water heating pipes, because I couldn’t get to that former closet to run any new wiring.
One outlet down, the rest of the upstairs to go.