I guess one way is to look at the Tormach manuals to find the wiring diagram for a machine that used them
but if I had them, I would look inside the driver and trace the connections between the 10 pin connector and the 3 input opto-isolators
you may find its something like this :-
with common +5V terminal pins connected together for all of the opto-isolators and 1 or 2 pins connected to each step , direction & enable input input
very often the enable input is a negative logic input so the drive will be enabled with no input !!!
Hi resolution pictures of both sides of the board could make it possible to work out how the 10 pin connector is wired
John