Thanks Stirling,
Here is the circuit associated with one of the input pins on the Motion control card.
If I'm correct, all the inputs have Schmdt trigger control, so by hooking up your opto circuit to one of the input pins should do the trick.
Is this arrangement correct.
I was confused because Arturo has a C3 index pulse board specifically for reading pulses from the spindle when threading on the lathe. I can only assume then that his Break out boards do not have the same Schmdt trigger arrangement on his input pins. Wrong or right ??
Thanks
George