Steve,
On page ten (10) of the LM technologies lm 48 manual it documents the baud rate setting commands. If the baud rate settings are not correct for each individual machine you will have communication errors etc...
I see the default setting for the LM 48 is 19200 bps , the default bps speed for many machines may be 9600.
See attached image for a basic Fanuc setup.
Jeff...