I am new to this.  I will research and be back tomorrow.  Thanks

All two of them.

OK, now I have installed my turnouts and find that the loco frequently derails on it.  I can't see anything wrong.  Any advice?

Thank you all.  This sure is a helpful forum.

I recently bought a Bachmann starter set with the 44901 command control center.  I got it working fine with basic features (e.g. whistle, bell, reverse, etc.).  I then purchased some turnouts on ebay.  These turnouts have green wires that connect to the turnout controller and a red wire with two spade connectors.  There is no place on my command center to attach these connectors.  From other forum topics I gather I need to purchase another controller (e.g. 44212) that has a place to attach accessories (AC).  My question - does this second controller plug into my 44901 command center or do these two controllers operate independently.  In other words, will I have to operate accessories with one controller (44212) and the locomotives with another (44901)?