I know that USB cables usually have 4 wires - power, ground, data+ and data-.

In this optical mouse cable I have there is a 5th. It is black, but also thicker than the others, almost suggesting that there is more than one wire in it.

What is it? My best guess is that it is another kind of ground wire.

Optical Mouse Cable from PCB to USB


That would be the cable shield, which is connected to USB connector metal chassis.

  • \$\begingroup\$ Looked up USB shielding, it's for reducing electromagnetic interference. Thanks for answering! \$\endgroup\$
    – Hari5000
    Aug 7 '20 at 8:55

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