Probably just their abbreviation for Spindle/Torch Height Controller cable (it’s function, not a cable type).
From your VFD to spindle you will need a 4 conductor shielded (preferably high flex) cable, probably around 16-18awg. From controller box to VFD will depend on whether you are using rs485 or PWM control, but these will just be a couple pairs of wires (spindle on, spindle clockwise) and another pair (0-10v, for PWM). These can be shielded, but it’s not critical here. The signals are low level, 22awg wire is sufficient.
Your VFD manual should be consulted for exact requirements.
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