Where do I find ARC starting signal - Stahlwerk CUT 60 P Digital

Hi everyone,
I'm currently building my plasma CNC setup with LinuxCNC and need some help with wiring. Maybe someone here has the same plasma cutter.
Hardware:
- Plasma cutter: Stahlwerk CUT 60 P Digital
- Motion control: Mesa 7i96S
- Voltage sensing: THCAD-2

My main question:

I'm trying to understand where to find the ARC starting signal on my plasma cutter. The signal that tells LinuxCNC: "The arc is burning, movement can begin."

In many tutorials or forums, I read about a dedicated ARC OK output on the plasma.
(See Attachment: the plasma cutter signal control has 4 pins 1, 2, 3 and 4)

On the Stahlwerk CUT 60 P Digital, I only find:
1. THC interface
2. The control socket (where the hand torch trigger normally plugs in) (pin 3 and 4)
3. I can´t find pins 1 and 2 or find anything to how to get the arc signal otherwise 

My specific questions:

1. Does the 2-pin THC output not only provide the voltage for the THCAD-2 but also a signal that tells me whether the arc is stable?

2. Do I need to get ARC OK somewhere else? I read in another forum that some plasma units don't have a dedicated ARC OK and you have to use a current sensor (e.g., Hall sensor) to detect whether current is flowing. Could this be the case with Stahlwerk?

3. What about the control socket? When I unplug the hand torch from the control socket, I have the contacts that previously connected the trigger. Does the Stahlwerk send any signal back through this socket that I could use as ARC starting signal? Or is it really just a passive input for the trigger?

4. Generally what should I do?

What I already understand:

- The THCAD-2 connects to the THC interface (the 2 pins) and then to the encoder input of the Mesa 7i96S. That's for THC voltage measurement.
- Torch start/stop ill get it directly of the cable
- But what about ARC starting signal output? How does LinuxCNC know the arc is actually there and can safely start moving?

How would you solve this with the Stahlwerk CUT 60 P Digital?** Is there a hidden ARC OK output I'm missing? Or are you all working with a current sensor?

Any help is appreciated – photos or pinouts would be great if anyone has them!

Thanks in advance