The B port connection has 2 physical ports.  There is a splitter cable for the B port connection on a 252 that allows use of both B and C ports at the same time.  My system is an RTK system.  The RTK correction signal come IN on the B port.  The A port goes to the Autopilot.   I then use the C port for anything else in the cab that uses GPS.  I run Sitemate times and I use a Loop Skytrack speed sensor.  They require different port settings so I am changing the C port quite often.

I am in a unique situation in that I not using the standard method of receiving the RTK correction signal.  To use AgRemote on the FMD, you have to set the unit to "auto configure" the GPS receiver.  When you do that, it puts the standard settings on the B port.  I am not using the standard settings.  So, if I want to configure the C port I have to let the unit auto configure so that I can use AgRemote.  When I do that it changes my B port settings.  So I have to set the setting I want on the C port, then change the B port settings back and then turn "auto configure" back off.  This requires a couple of reboots on the FMD to accomplish also.  It ends up taking about 5 minutes to make a change (if you don't forget to make a setting the first time :-(........)  I wish they had a version of AgRemote that would run on a PDA.  It would be easier to connect my PDA and run AgRemote thru port C.

The FMD display is like the Insight in that you can not run other programs.  AgRemote is included in the User Interface of the Trimble Firmware.  You are able to access it from the Setup section of the FMD firmware.