Trains Compatibility?

[AshleyAshes]

So, I lost all of my legos from child hood years ago and I started collecting sets agian, soon I'll have enough to start building my own works from them. One thing I have an interest in are the Lego Trains, and the center piece of my little collection is the PF Passenger Train. I wouldn't mind collecting or building additional train elements.

My question is, how far back does the compatibility go for Lego Trains? Are the 'RC' trains that came before the PF system compatibile with each other? That is, the tracks and the couplers? (It's obvious that their method of control wouldn't be compatible unless I swapped out their motive gear)

That Santa Fe set for example, while expensive on eBay, is pretty cool looking but they're 9V sets using powered rails. It's obvious that a 9V train that got power through electrical rails would never work right on plastic rails, but could the cars themselves fit current tracks and mate with current couplers?

Also, the connection between the 9V track segments and the current PF segments look the same. Are they intercompatibile? Agian, I know the plastic tracks couldn't conduct power, but could the old metal tracks run current PF trains?

[dr_spock]

The track gauge are all the same. You can run PF trains on 9V tracks. The couplers are compatible too.

People have converted 9V trains to PF and PF trains to 9V.

[AshleyAshes]

The track gauge are all the same. You can run PF trains on 9V tracks. The couplers are compatible too.

People have converted 9V trains to PF and PF trains to 9V.

Great, that's what I wanted to hear. I was failure sure but I didn't want to eBay something and then set it on some tracks only to be suprised that it wouldn't run. Thank you very much. :)