Look what I found! http://hometown.aol.de/redrockrail/English/Digital4.htm A full instalation guide for my z-scale AZL SD45! yes!!! It's for Selectrix...and it's the only one I can find that is able to fit in my SD45, so it's gonna be Selectrix then. ...but on a other site I read "for all DCC systems" so I could use it with Digitrax, maybe? , I'll investigate.