Pinout Apc Serial Cables
PinSignalDescription1Shut Down (dumb mode) / In (smart mode)Set high for 1-5 sec to activate shutdown.2Line Fail (dumb mode) / RS-232 TX Out (smart mode)On-battery power (normally low but goes high when the UPS switches to batteries)3Line Fail signalMains down (normally low but goes high when line fail)4,9GNDGround, chassis5Low battery signal(normally low but goes high when low battery)6Line fail signalInverse of pin 2 Line Fail signal7UPS Turn-on/off signal(on advanced UPSes only)8Unregulated +24 Vdc Out??
I replaced my old APC SmartUPS 620 with an updated model. I had lost the serial cable that allows you to communicate with the UPS via a computer for the old unit. The new unit came with the serial cable and for a while, I was looking for the correct pinout so I could build a cable myself. So I wanted to get the pin out documented. The cable is a male to female DB9 cable.
Well I got my voltmeter and using the continuity setting I mapped the pinout. It would not be difficult to create this cable. Many of the cables DB9 serial cables I had laying around were female to female and it was hard finding a male end. Hopefully, this will help others out there that need this cable and don’t want to pay $30 for it.UPDATE: I have updated the diagram based on the comments I got on this post. Apparently, I counted the male pins incorrectly so I made the correction.
9 Pin Serial Pinout
Pinout Apc Serial Cables Diagram
Thanks for your feedback.