When I use a 12kHz TTL signal from my Function Generator, the relay works fine. However, when I use the 12kHz signal from Mach3, I get the spastic relay. I scoped the Mach3 signal after passing through the transceiver, it appeared to be a good 12kHz 5V to 0V signal.

I am going to run the Function Generator signal through the parallel port as if it's Mach3's, and thereby through the tri-state transceiver. I'm narrowing it down and will find it.

Thanks for letting me vent.