I think I've answered my own question with this link. https://electronics.stackexchange.com/questions/303305/why-is-an-ethernet-cable-not-grounded
> -----Original Message----- > From: John Dammeyer [mailto:jo...@autoartisans.com] > Sent: September-08-19 8:31 PM > To: 'Enhanced Machine Controller (EMC)' > Subject: [Emc-users] MESA 7i92H Power > > Quick question. Running signals from the parallel port to the BoB definitely > couples the PC Ground into the Bob. Generally then the BoB optically > isolates the PC signals from the rest of the system Or expects the motor > driver to do it. And for the rest the BoB is supplied with an isolated supply > that is not connected to the PC side. > > Since Ethernet runs the 7i92H and it comes from the PC does the 5V power > into the 7i92H have to have the 5V DC Ground common with the PC DC > ground? Or can the 5V be derived from a 24V power supply whose ground is > not common with the PC ground because there's no direct connection. I > recall something about PCs using transformers inside the RJ-45 Ethernet > connector but I don't remember for sure. > > John > > > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
