Question about using the "VH" command with a plasma cutter.

Hello all! I have a question about using the "VH" command to raise and lower the torch while cutting.
According to the manual, while in height control mode, the z axis raises if input #1 is low, and lowers if input #1 is high.

So what happens if I just want the z axis to stay steady? Do I send input #1 a pwm signal with a 50% duty cycle? If so what frequency of pwm would I use?

Thanks all!