I recently acquired an Systro 4 axis CNC table with DC servo system (ISEL PVD servo driver unit, SKC DH series servo motors). The servo driver unit has a 50 pin connector with a pin for each of the axis described below:

Index +
Index -
Track A+
Track A-
Track B+
Track B-
Analog Input (Control voltage)
Reference switch pin
limit switch positive
limit switch negative
(attached is full pinout)

I am new to CNC machines and from the research I have done so far, I may be able to get a USB interface board and use this setup with Mach 3 software. However, when I look at the specs of some Mach 3 USB interface boards, I can't tell if they can be used with my system or not because I don't know what the pin names in my system do (ie, index pins vs track A/B pins).

I am looking for some recommendation as to which mach 3 USB interface board would work with my system and also some help to understand what the index (+/-) and Track A/B pins do. Any help is appreciated.

Thank you.