I found this manual for THC Robot 3t on this link
http://www.variometrum.com/PDF/USER_MAN ... P_DOWN.pdfIf I understand this manual correctly,
Parameter 1 (Set-height), from the image you supplied, is for setting the working voltage (torch height).
Parameter 2 (Area for control) is settings for ARC OK signal. For example: If parameter 1 is set to 125 and parameter 2 to 30, this means that the ARC OK signal will only be active if the voltages range from 95V to 155V.
Parameter 3 (Sensitive) is something called "dead band" as Beefy wrote in the previous post. This parameter determines the sensitivity (response of the Z axis) to changes in plasma arc voltages.
Parameter 4 (Arc-voltage), as indicated in the manual, shows the plasma arc voltage.
Also in Mach3 go to config / ports and pins / mill options and turn on Allow THC UP / DOWN Control option even if not in THC Mode.