Not sure on EA's, but on my xa the NSS has four wires - two for reverse, two for ignition kill in 1,2,R, and D. On the xa power runs through the NSS, to the indicator assembly where it is sent to the two rear indicators. All the wires are red and black.
Stick a multi meter on the NSS, and play with it. you will soon work out what is what.
I spent a full day trying to figure out why my reverse lights would not work, before cracking open the NSS to find the contacts were good enough to give a voltage reading on the multimeter, but just worn enough to prevent any meanigful current going through to the reversing lights. I went through three switches before I found a good one.