I just bought a Leica GFU29 modem for my ATX1230 GPS with RX1250XC controller and I can't for the life of me figure out how to get connected to the internet and NTRIP castor to get WSRN (WA State Ref Network) Real-time corrections. I have an AT&T sim card that my company sent me, which should be activated. I know it's probably just something simple that I'm missing but could really use some help with the configuration!
I don't have that 1200, but do have the GFU29's working on the GX1230's. There are several things to solve, starting with a data connection on the network, then configuring an internet connection and finally configuration set to use that connection. This link will take you to some useful howto for the ORGN with a Leica 1200 and with the appropriate changes for the WSRN may be a good help for you.
SHG