[rodw]

I'm not admitting I'm asking, I don't know how it works and you seemed like you know, so I asked how that works.

THC hardware just measuring voltage and generating the THC up and down and arc ok signals. You have to have a hardware which measures the arc voltage, I mean you need that with linuxcnc too right? Or you connecting the hundreds of volts directly to the computer?!
My understanding is that the motion controller is controlling the THC with Mach3 and UCCNC so it is realtime on the motion controller. I guess voltage could be also digitized into the motion controller, it has 2 analog inputs, but I did not try to use that because I have a THC controller.

Thats my point. You only need to send the divided voltage and ArcOK to Linuxcnc and the motion controller can directly control z axis torch height instead of using a rather crude method of generating up and down signals for the reasons outlined so eloquently by Peter from Mesa in a more recent post. But not only that, you can build vastly more sophisticated control such as velocity anti dive, kerf crossing, auto torch sampling etc into the

motion control setup that has direct access to all real time motion in an environment with almost unlimited memory and CPU horsepower