Excuse me,
The PC parallel port outputs a binary signal, meaning it has two levels, off / on; or 0 / 1. The 0 is represented by a voltage less than 0.8v The 1 represented by a voltage greater than 2.4v.
Because the signal of interest is a PWM waveform, the voltmeter will be showing the average of the highs & lows of the signal. PWM means Pulse Width Modulation. By varying the proportion of ON time to OFF time in a given interval (20ms) the resulting effect is an analogue voltage. If the ESC wants a true analogue voltage input, a small value capacitor (1μF) between signal pin and ground will help.
If you have access to an oscilloscope this would all be really clear.
Thank you class for being attentive. Now, run along and play with your nice machines!

Oh! I just answered my own problem! Use the oscilloscope to monitor the output of the PWM line (from Mach3), and see how similar it is to the DCBLM drive module requirement!!