Wiring of servo spindle - MESA 7i76E

PS - you don't need shielded cables from the contactor/breaker to the amp.  Just from the amp to the motor.

240V-in (unshielded) Main disconnect (unshielded) Breaker (unshielded) Contactor (unshielded) Line reactor (unshielded) Amp (shielded) Motor
 

Thank you so much for all the info. This certainly gives me a bit to chew over the next weeks.

Thank you for the recommendation in your last post - very handy.

deus wrote:

• What is the typical fault signal called within Linux CNC that would be good to trigger the physical e-stop loop?

Possibly halui.estop.is-activated but that is from halui so not real-time. 
linuxcnc.org/docs/stable/html/man/man1/halui.1.html

I would start by looking to see if motion.motion-enabled has the desired behaviour:
linuxcnc.org/docs/stable/html/man/man9/motion.9.html
That's from the motion module, and should be 100% reliable even if the GUI crashes. 

You can use halmeter to watch how pins change state. 
linuxcnc.org/docs/stable/html/hal/tools.html#_halmeter

You might also need:
linuxcnc.org/docs/stable/html/man/man9/estop_latch.9.html
 

it is called Analog servo interface , this card will explain

www.mesanet.com/pdf/motion/7i33man.pdf