The back of our APC Smart-UPS 2000 has a USB port so that it can be monitored from a server it supplies.

However, this USB port doesn't appear to be a standard USB connector. It looks a little like an RJ-45 connector, I tried an Ethernet cable in case the port was just mislabeled but that didn't fit either.

Strange USB port

Can anyone help identify the type of USB it is?

  • 8
    @JakeGould It's likely a legacy format rather than a licensing issue. RJ-45 connectors for serial ports have been around a long time. I know as recently as 2010 I had Cisco gear on my desk that used an RJ-45 to serial adapter to get a console connection. This question should help clarify serverfault.com/questions/629436/…
    – Freiheit
    Dec 5, 2017 at 19:05
  • 32
    Technically that is an RJ-45. It just happens to be wired for USB instead of Ethernet. Dec 5, 2017 at 22:45
  • 9
    I bet someone got a really nice bonus for that feature. (To quote Raymond Chen) Dec 6, 2017 at 1:14
  • 8
    Fun fact : USB male fit into a RJ45 slot. So when our user says "yeah I plugged it in" don't trust him...
    – Goufalite
    Dec 6, 2017 at 8:15
  • 2
    @Freiheit RJ45 serial connectors are very common on enterprise network gear. My (freshly bought) Ubiquiti EdgeRouter Lite has an RJ45 serial connector.
    – Eric Brown
    Dec 6, 2017 at 21:54

2 Answers 2


That is a port for a UPS Communications Cable Simple Signalling - USB to RJ45 cable for connecting to a computer. The cable is included with many compatible APC devices.

UPS Communications Cable Simple Signalling - USB to RJ45 cable


That is an APC cable by Schneider Electric cable P/N AP9827


It looks like half an Ethernet cable with just four wires in 1 3 5 6 enter image description here

APC's user manual from one type of UPS is downloadable at: http://www.apc.com/salestools/JGNY-9X784R/JGNY-9X784R_R0_EN.pdf

And an excerpt with that connector is:

enter image description here

  • 3
    Very funny the fact that the DSub-9 is often used for serials but cannot be used with normal cables and the RJ45 is totally seldomly used for USB. Insane hardware of the past.
    – eckes
    Dec 6, 2017 at 5:51
  • 13
    @eckes insane hardware of now - this is pretty much standard on UPSs. Dec 6, 2017 at 8:48
  • 5
    The UPS might be sold to a few customers that specify connectors to physically lock - which RJxx does and USBxx does not. Also, "generic" USB cables might be undesirable in environments where eg flammability standards are to be adhered to... OR, there are two versions (one with another serial, another with a USB port) sharing the same faceplate... Dec 6, 2017 at 16:11
  • @eckes I had to wire a cable for a UPS years ago. From memory the circuit was just 4 resistors and swapping some wires in a RS232 cable. The reason is that the D-Sub9 port on a UPS is a control port, not a serial comms port, and D-Sub9 is just a generic connector design, not specifically for RS232 serial comms, even though pre-USB it became the most common serial connector for PCs. I haven't worked with UPS for years, but I had the impression everything had been redesigned to use standard serial comms. Interesting to see that the old designs persist on some devices Dec 9, 2017 at 12:33

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