Confused as to what J20 on Sound Logic board does...

The manual for this board does not make very clear what/how this this
works.

Can I use this for an "input" from the err/reset of a Gecko 320/340?

My plan is to create a circuit like the one in the gecko manual with
an emergency estop button that should simultaniously shut down the
drives and tell the PC (Mach1) to estop.

It appears that the J20 on the sound logic board is wired to pin 10
on the parallel port, but it is not clear if this is an input or
output.

Can I use this connector for the above described purpose?