wiring 45n gateman with common ground and direct power?

Ok well the excitement got to me so i rigged it up and look at that, it works perfectly!  Fantastic, no fires and no explosions.  Hopefully there isn't anything I've missed. 

Follow up question, at the moment I'm wiring into the variable voltage posts on the 4090, with U going to the outside rail.  Would it be possible to wire the same way using the fixed voltage arrangement?  B and C provides 11 volts which is working well.  On the post about wiring multiple transformers all to the same common line, I think he mentioned doing it with the fixed voltage as long as the transformers are not wired in parallel.  This is where i really start getting confused, I'm used to using at least one post marked U.  Does it matter?  Since AC is apparently switching the current back and forth, is there even actually a "ground" vs "hot" or is that something we use to keep track of the wires?  

Also, the common post on the 4090 is "A", not U.

Dale, I hate to sound silly, but can you explain the benefit of relays in layman's terms?  I'm understanding that it functions as an electrical on/off switch, but it seems like a different way to do the same thing I was already doing.  I don't understand what you mean by arcing, are you saying that there may be an arc from middle to outside rail, from insulated to non insulated section of track, or little lightning bolts running across the axles causing etching or something?  What exactly is the benefit of a relay, which there must obviously be.  I ask because I want to know WHY I'm doing something, help increase my knowledge base.

I was looking for this online, I saw 12/2 Romex by Southwire, is that the stuff you mean?  I'm not catching what you mean by "6".  Now, the Romex has three wires in it, are you using the 3 wires separately starting from 3 different transformers, or are they all beginning from the same post?  I guess this is a style question. 

Rob, I've read a lot of your posts and I'm honored to see your input.  Since I have almost no electrical knowledge, you just turned my world upside down.  I assumed that U would be the common post for all transformers, why on earth would they change that?  So I'm guessing that if I'm tying a 4090 into a common bus i have to use the A post, and the U post goes to the hot bus?  Man, it seems so wrong, why would Lionel do this to me?

If I wired my 45n the same way as the OP did but used a ZW and used one of the accessories outputs, would that be safe?

Ok, while doing some embarrassingly basic research on relays, I found this line interesting: "Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits)"

So I take this to mean that the answer to my question, why use relays, is that I can wire in a higher voltage circuit for the accessory through the relay, and use a low voltage signal from the track to trigger the relay, without worry of the accessory voltage interacting with the track.  In exaggerated terms, I could have 14vac going to the Gateman, and the relay would trip with only 5vac (an exaggeration I'm sure, but just to make a point), and I wouldn't have to worry about the 14v for the Gateman somehow jumping to the 5v on the track, which I think is what Dale is referring to with regards to arcing. 

Does this sound correct?  Thanks all!!

Dale, i sent you an email to the account listed on your ogr profile, hope you don't mind.  In case you don't get it, the question i asked is what kind of relays do you use?  i searched for 12v relays on ebay and saw parts for car alarms or stereo systems, are these the ones you mean?

Thanks.