After suffering a bad manufacturer-configuration related crash, I decided to basically re-engineer the machine after discovering too many problems everywhere I looked.

For alarms I decided to go with the failsafe method of normally-connected high (+24V) / active-low (open connection), and hook them all in series along with e-stop.
I decided to just use estop because I want to keep things as simple & failsafe as possible and don't have a lot of spare controller inputs.
SO far I've successfully hooked up & tested servo fault alarm outputs and it works well.
Now I want to add VFD fault output into the alarm chain. But I'm not an electrical engineer and am somewhat confused how to accomplish this.

In my case I'm using a Fuling DZB312B005.5L2DK VFD.
Among other issues I've had stop-braking trigger E00A (over-current) alarms that could result in an undetected tool start failure and a crash.
The manual seems to imply that parameter F2.21's default value of 3 will drive an open-collector signal between A, B, C outputs. (?)
Which outputs are NO which are and NC is completely unclear but I surmise it's A-B=NO & B-C=NC or the reverse.
I can't just check resistance with my multi-meter because it needs power but I'm afraid of hooking it up backward or somehow mis-wiring & damaging hardware.

So my question is, how should I wire this in to my alarm chain of open-collector outputs (effectively NC switches)?
Can I just hook the hook the end of my chain (which normally is +24V) to B and read C on as the estop (aka alarm) input on the cnc controller?
Or is it the reverse?

@mactec54, you seem really knowledgeable about these VFDs. Thanks for your help in the past! Do you have any suggestions or advice?