I found this article (SCART - Wikipedia) on wikipedia & that seems not present in TVs I've seen so far.
It's just a connector standard (and not a very good one) - the signals are still 1V p-p into 75 ohms, same as RCA.
My adapter is just a SCART plug with RCA sockets on the back. It has no active components inside.
Also I found some PIN change setting over another picture I got over google.
I have no idea what that means.
In my experience, old-school analogue (CRT) TVs are more forgiving of slight deviations from signalling standards that you sometimes find with software video implementations, but I've had no problems with the TVout library into more modern digital sets.