So if I understand well i need to connect the USB UIRT by usb to the core/hybrid and then when I for example issue a command from an orbiter the USB UIRT will send it to my external box?
Yep, and when that works, the world is a wonderful place! This works even if you're watching LiveTV on a different computer... if it's pulling the feed off that box, the channels will also be changed on that box.
Could it be possible that it would not work with any/with my box cause I am not in the US or UK?
Yep, success sometimes can be a coin toss.
Perhaps you specify (if you haven't already) exactly what cable box you're dealing with, and where (city/country) and maybe somebody here in the forums can be very specific for you.
...Do I have to follow what is written about TuneToChannel.sh ? Cause as a linux newbi I understand very few of it.
And the i read something about "how to get the USB-UIRT to actually learn codes".
Yes, once you have the USB-UIRT installed, you will then add your cable box as a part of your A/V Equipment. If there isn't a template for that particular device, you can create one, and have the system "learn" the IR codes, to control your cable box, by using the web admin wizards... you will be able to have it "record" the IR signal for all your numbers, the enter key, etc.
Once you have that template created, jump into the A/V Wizard from the GUI and tell Sarah what connections are going where (I found it easier to do it from there).
Then, when you find the deviceID of your cable box, and the sourceID for your program guide, you can put that TuneToChannel command into the MythTV Setup program, under Inputs...
And then, magically, when you are watching TV and change channels, it should send the correct signals to the cable box, so it changes to the correct channel.
It's amazing when you see it all work.