Well guys, I'm confused. Listen to this:
I have one "Expert" transmitter that I'm told it really a JR Tx.
I have a Sanwa transmitter that supports both shifts.
And, I have a JR receiver (R700).
I tested that my receiver actually works with both transmitters (Sanwa in PP mode).
I verified that the receiver does not work with the other Sanwa mode.
What I'm saying is - I verified that both Tx work in the same mode.
Now guess what - according to what we all know, and to the excellent description by Phil, one of my transmitters in Futaba while the other is JR. This is of course nonsense.
I think that one of the cables is reversing the signal. Which leads me to the conclusion that you cannot really tell if your Tx is Positive or Negative by just using an oscilloscope - you have to test it with a receiver.