I have never tried to control a Samsung via serial so I have no first hand experience, but I believe the settings are 9600, 8, None, and 1. Make sure you have the correct address set in the display itself, as that is part of the command string. For address 10, enter 0A; for address 75, enter 4B. I believe straight connection, not a null is needed. Have you tried to using Hyperterminal or any other program from your PC to see if you can get a response? Have you verified the CM-232 is working? I've had one or two of them go bad over the years. Is there another device there you can try it out on, or another CM-232 cable you can swap out? Hope this helps.