This unit seems to have good Mach3 support.  Has anyone tried this relay?  If not what have you used with good results.  Thank you.
http://www.easy-cnc.com/relayboard.html  I have no affiliation.

The thing I always get a kick out of is,  that break out boards such as this advertise complete isolation between your PC and coolant pump, router etc, if these are mains fed motors, whether 120v or 240, they will be at the same potential as your motherboard power supply common.
This is due to the motors having a grounded neutral and the custom of PC's to make the PC P.S. common to ground, this will obviously apply to the P.Port  common.
So it is not isolation, just a method of switching one source with another, USING opto isolators.
Nosmo.

Indycraft,

You may also want to read this posting / thread for some more info  http://www.machsupport.com/forum/index.php/topic,15369.msg103352.html#msg103352

Tweakie.