Hypertherm powermax 65 ARC OK

START is the input to plasma from a relay on the break out board, TRANSFER is the ARCOK signal that goes from plasma to BOB or to THC depending on your setup and type of THC, Voltage Divider is the output goes from plasma to THC voltage input usually 5V.
Give us more info, so we can better explain.
Regards,
Tom

Proma THC SD does not have an ARCOK signal output, it has that internaly linked to start correcting the torch height on it's own, so Linuxcnc does not know if the torch has fired, but you can do some tests and add G04 P0.2 for a 0.2 sec pause after the M3 command or whatever you find works best.
You can not use the THC config from my post with THC SD, only THC 150, and all the explanations and how to modify it to your needs are attached with the config.
Regards,
Tom

Yes you can and you should since you can use a regular linuxcnc config and just add the motion hold until it gets the ARCOK ( or transfer in your case ) to start moving. That would get rid of the pause i mentioned in a post above for thinner materials, on 5mm and above you would still need the pause for piercing.
Did you wire the THC SD already? it is very simple to wire up, but i sold one and i had to go install it since the person that bought it thought it was way to complicated !!! It is very simple and it works like a charm.
Regards,
Tom