I'm not sure I understand anymore. The current goes the way the diodes face even If it is AC. Now Im looking at the output terminal as the 3rd output because it would need a positive charge to go through the diode and the resistor is the Load. I'm saying that since RL is the load wouldn't it be the output terminal. For the output as 1, I don't really see how it could be since on the next half cycle it becomes negative as in output 2 alterations. I thought the current would start at the center tap? I understand it as the current goes through the center tap, output 1 and 2 fluctuate between positive and negative, that eliminates them as the output terminals. Output 4 is after the load drop which makes it negative and output 3 is positive because it is positive before it goes over the resistor.