When you get access to the train on the wall you well see a panel with 3 rows of switches. You have to look to the right of the panel there is a sign, look at it. There is a series of numbers on the top right, copy it down but beware some of the two's look like Z's. Now go back to the panel. Copy what you wrote down start at the bottom row go all the way to the end and copy what you wrote backwards on the panel. If you do it right a green light will appear on that row.