While cleaning up the office today we ran across two odd looking cables still in bags. On one end is a female DB 9 connector and the other end is a 3.5mm plug with 4 contact points. The types of equipment we have are: Dell workstations and servers, HP SANs, Equallogic SANs, Cisco network gear, and symmetricom time servers.

The only thing I found on the net is a speakercraft adapter cable but we've never had anything to do with speakercraft.


UPDATE: We don't have any cameras or video/audio equipment in the area. It can't possibly be for a camera, cell phone, or some other home consumer item since we just can't have that stuff in the area.

  • 4
    Pictures! Post pictures. Mar 25, 2013 at 20:27
  • No cameras or cell phones allowed in here. I'll take the cable home and upload a picture in about an hour.
    – murisonc
    Mar 25, 2013 at 20:35
  • One of these? cablestogo.com/product/02444 Mar 25, 2013 at 22:14
  • Nope, that one only has three conductors on the plug.
    – murisonc
    Mar 25, 2013 at 22:25
  • 2
    Throw them all away - within 15 minutes of the garbage truck driving away, a critical piece of equipment will explode. Then you'll know!
    – Dan
    Mar 25, 2013 at 23:09

7 Answers 7


I finally found them. The cable is a firmware upload cable that came with our IOGEAR GCS1644 KVMs.


We've had them lying around too. They're usually thrown in the box to give you serial console access to a wide variety of gadgets. Have a look for ISDN terminals, video projectors or UPS devices. Could even be a graphing calculator!

  • 1
    +1 for calculator - fairly sure a TI83 I had years ago had a cable like that Mar 25, 2013 at 23:49

From the depths of my grey mind I think there's a possibility that it's something used on a VERY old HP MSA SAN array (maybe an MSA 1000?). Happy to be wrong but I'm sure I've seen one years ago like that.

  • 1
    I definitely have a disc pack that uses this for console access, but it's in a colo on the other side of the country at the moment, so I can't go check what it is.
    – MadHatter
    Mar 26, 2013 at 8:54

In some cases, it is a specially made Video Cable for Polaroid®'s PDC-300, Fun! 320, & Fun! Flash 640 cameras.

  • It might be for a digital camera but not necessarily a Polaroid. As I recall this was commonplace in the pre-USB days. Mar 25, 2013 at 21:05
  • Those are all 3 conductor plugs aren't they?
    – murisonc
    Mar 25, 2013 at 22:09

I have one. I mean identical in appearance -- even the mounding of the connectors appears exactly identical.

What I know is we have UPS devices, old APC Back-UPS, etc., but all of them seem to have DB-9. Then we have various generations of KVM switches, but not the manufacturer mentioned having such a port that is unexplained by audio connection. (This would not be audio--nobody in his right mind would hook audio to db-9.) We have iPod, iPad, and iPhone -- but never recall purchasing a cable like that. However I see on eBay such a cable of nearly identical, but metal connector, sold as a "data cable" for iPhone/iPod/iPad. Can't find any documentation to support, and the sale gives none whatsoever.

Another possibility--I have a very old digitizing tablet, separated in location now. (Will relocate in next few months, then can check if fits.)

I present all this for possible elimination. My memory was an older UPS, but can't find one that matches.


many mobile devices use 3.5mm jack for serial console. my bet is that if you open the DB9 housing - you will find a TTL-to-RS232 convertor chip in there


(from a buddy here at work, but sounds right, hope it helps)

There are lots of different applications for a DB9 to 3.5mm plug.

RS232 serial control is my bet here in an IT shop. A 4 port/conductor 3.5 will typically be audio (stereo) plus video (or maybe bi-directional audio, think output and input). For instance, an iPhone uses a TRRS (4 conductor) for the headset. Look for equipment like touch screens, custom hardware, camcorders, etc. that would require a db9 to 3.5mm.

  • We've looked at everything we have. No cameras or personal electronics are allowed in the area.
    – murisonc
    Mar 25, 2013 at 22:11
  • Another thing that came to mind...what about a music-on-hold device for an older PBX?
    – TheCleaner
    Mar 26, 2013 at 14:28

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