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.