I understand the standard decoder connections and what they're for. The red & black are quite easy to determine how they're connected. (left & right track pickup). However the grey and orange are the + and - connections of the motor. This will determine which direction the loco goes in "forward" (or "reverse"). Is there an easy way of determining what connection to the motor is + and which is -, other than trial and error? What method do you use, if any? 3 out of the 4 decoders I've put in so far, I've had to reverse the grey/orange connections to get the right direction of movement. I just made a guess as to which was + and which was -, as I can't think of an easy way of determining this.