I'm a little late to this party, but have been working on a similar (DIY 4th axis integration) on my own. I can confirm (and have verified with Tormach) that the information in the Series 3 manual that SwampDonkey copied above is INCORRECT. The Direction, Step and +5V signals can be found on pins 3, 4, and 5 of the 2x5 IDC (ribbon) connector.