We talk about 0 and 1 but often they are voltages. So what is zero and one.
RX- is the base voltage. So by examine RX+ you can say does RX+ = RX- then zero otherwise if RX+ is significantly greater than RX- then one.
So the word significant means that RX- and RX+ are different enought not to be caused by natural electrical properities of the cables and connectors.
Obviously it is a bit more complex than this.
I had always thought that TX+ and TX- represented the differential pair that comprises the TX signal. Since all CAT5 etc cables are done in differential pairs this was how the individual signals are labelled.
Thus TX+ is the exact opposite of TX-. The two combined will give you zero but fed into a differential amp and you have a signal. Thus noise induced on both cancels out whilst signal that is opposite on both carries through the amp.
Does that sound right? Obviously same goes for RX. I guess I'm saying the same thing as you but from a different angle. My understading was that if TX+ == TX- then that didn't mean anything signal wise and that it was more like TX+ == 12V and TX- == -12V gives one symboll whilst , TX+ == -12V and TX- == +12V gives the other.
Though my manchester encoding may be getting foggy...