I don't think its the only device that would work, just happens to be one that we know will work. I've never heard of or used a "MOXA" product. I guess other then outputing the SMDR for call accounting systems, we've never had a printer tied to the system for alarms and such.
I guess I'm still confused as to what your connecting to what. The original link you posted goes to a USB to serial devices. Are you trying to conect the multiple serial ports from a controller to a computer? If so, why not just open multiple telnet ports to watch the same information?