Thanks @ Martin Philip and olivier_robert;? Yes, from the documentation it seems like it should work with the FF commands. However, my attempts thus far have been unsuccessful. The best I get is an acknowledgment.
Example: input selection
# sending "xb 1 90\x0D" => to select HDMI1; TV replies with "b 1 90\x0D" ...and TV switches to HDMI1, if not already selected
# sending "xb 1 93\x0D" => to select HDMI4; TV replies with "b 1 93\x0D"? ... ...and TV switches to HDMI4, if not already selected
# sending "xb 1 ff\x0D" => to query input, TV replies with "b 01 NGffx" in all instances.
=>? Has anyone of you 'real' feedback actually working? There is a good chance that I have missed something.
PS: @Martin: I will check out your quick fix. Thanks!