I built a circuit board using a 4001 IC ( flip/flop) to light a red or green LED to indicate which mode the switch is in. It works OK but the LED's flicker when the train is running. I am O gauge with post war Lionel. I operate the switches off of a Post war Lionel ZW trans former. All 4 of the transformer power take offs work with a common ground. I think that is the problem. The circuit I used was off of one posted on this Forum. Any thoughts?