The first lesson from Chapter one of Eco’s book is recognising the difference between a signal and a sign.
A signal is “a unit of a system that may be an expression system or a physical system without any semiotic purpose…A signal can be a stimulus that has no meaning but causes something…”
A sign “is always an element of an expression plane conventionally correlated to one (or several) elements of a content plane”.
[OS not much understanding shown. Bit of regurgitation perhaps?
SS Yes, but if there was a danger signal on a train track I’d know to stop, if there was a sign in a newspaper about why the train was going to stop, I’d be able to take an alternative route.
So, I have learned something]