I was looking for an answer to the question how the 1000BASE-T transmission works and I came up with this post How does "bidirectional" transmission on gigabit ethernet work? but still a few issues it is not clear to me. If I understand your answers correctly, if on the two sides of the wire you receive a signal, say +1, each recipient will receive a +2 signal. The question remains: what happens if we send two signals say +1, -1 and on the other hand a signal with a value of 0 will be given in the same pair. Is this possible? If so, will the 0 signal meet the +1 signal and then it will meet with the -1 signal, so will the value we get will be 0? From the answers there, we get +1, but I do not know why. I decided to ask a new question because I have too little reputation to add a comment :(
In (a) the hand has waved up and down and a wave has started to travel along the rope. In (b) it's moved again and sent a second wave, as if corresponding to sending (+1, +1). You could imagine moving the hand down to send a -1 wave.
Multiple impulses can and will be in flight along the wire at the same time. Including reflections of your transmission from the other end.
The technique used is called echo-cancellation. It uses the idea that you know what you are sending, so you can subtract it from what you are receiving.
This paper goes into quite a lot of detail.