That interesting on the Mach 3 versions. I've been fiddling with this on and off for a while and must have got a little muddled up as once I finally got a setup that Mach3 could see (above) it turns out the active low setting is working just fine with both the probe and touch plate which is great. Now using each probe is just a matter of plugging in the one you want and off you go, fantastic. Thanks for the link to your write up, all interesting stuff.