Which is hot which is common?

Does this thread help? I haven't looked at one of those connectors in years.

https://ogrforum.ogaugerr.com/...ich-wire-is-positive

"The internal barrel is considered HOT (red) and the outside of the Barrel is considered common (Black).  So if your going to attach them without adapter find which wire is connected to outside barrel and that is black." per GGG

Just throwing this out there to spoil the fun, My Z1k came wired backwards from what everyone on this forum said it was supposed to be.  Might be worth taking a moment to check.  

If you have a multi-meter it is easy enough, but can be done with a light bulb as well.  With a meter, set to ohms, and the transformer unplugged, connect one side of the meter to the terminal marked as common, and then check both the inside and outside of the barrel jack with the other side of the meter.  whichever reads 0 ( or close to it) is the common.  

Without a meter, connect one side of a light bulb to the common terminal and see which part of the barrel jack makes it light up.  whichever does not light is common.

My z1000 came from the factory wired in such a way that this test would not work, as the hots were connected together inside so if your's is like mine, the test will be backwards.

  Black to outer rails, a test running conventionally, a transformer horn button should blow the horn; not ring the bell. (just incase that got screwed up too).

Thanks for the info, right now I use an old lionel KW for conventional control. My layout is under construction but far enough along that I want to test command control on it.