Some of the USB 2 extension cables in my collection have an extra sheath or shroud at the female end, with the type-A socket recessed inside by a few millimeters.

Is there a reason for this? Is it standardized or documented anywhere?

In the attached photo, from left to right, the type-A socket is,

  • Flush with the sheath, works with all plugs and devices.
  • Recessed about 3mm, works with most plugs and devices.
  • Recessed about 5mm, works with very few plugs and devices.

The cable lengths are approximately 32in, 16in, and 20in, respectively. They are passive extension cables.

USB Cable comparison

  • Note, I googled various permutations of "usb extension" with "sheath", "shroud", and "recessed", but I could not find an answer. – jamieguinan Feb 22 '18 at 21:57
  • One of those look like an active cable. What are the lengths of these cables? USB 2 or USB 3? – Ramhound Feb 22 '18 at 22:09
  • From left to right. 32in, 16in, 20in. USB 2. They aren't active, as far as I can tell. No enumeration when I plug any of them in. – jamieguinan Feb 22 '18 at 22:20
  • Update your question. – Ramhound Feb 23 '18 at 0:03
  • I suspect it has something to do with the fact these are extension usb cables, which I have only ever seen being active, as for the differences I suspect that’s linked to their length. – Ramhound Feb 23 '18 at 0:08

USB 2.0 extension cables are illegal from USB specification standpoint. This is because the extra imperfection along USB 2.0 transmission line causes massive degradation of signal integrity.

So no test procedures nor acceptance criteria are there, and anyone can craft whatever they feel. There are more variants of overmolds, like this one below. Use at your own risk. Works fine for me though.

An example of a USB cable without a protective sheath around the connector.

  • “USB2 extension cables are illegal from USB specification standpoint” Really? Can you provide some citations. – JakeGould Feb 23 '18 at 3:04
  • sdphca.ucsd.edu/lab_equip_manuals/usb_20.pdf - page 120 of the pdf (labelled page 92) under "6.4.4 Prohibited Cable Assemblies" - Ali's right here. – Journeyman Geek Feb 23 '18 at 3:29
  • Accepted this as it does answer "Is it standardized or documented anywhere?". Thanks @JourneymanGeek for the specific techinical reference. – jamieguinan Feb 28 '18 at 20:58

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