DATA, it’s legacy (1.0-2.0) USB’s differential pair for backwards compatibility. You only need one side to make contact so they decided to simplify plugs for devices that use the legacy mode. For example most mice and keyboards, even ones with USB-C, still use USB 1.1 because they don’t need the extra speed, and 1.1 cables are cheaper because the low speed allows them to be unshielded and still not suffer much interference.
What is D and why is there no second pair in the plug?
DATA, it’s legacy (1.0-2.0) USB’s differential pair for backwards compatibility. You only need one side to make contact so they decided to simplify plugs for devices that use the legacy mode. For example most mice and keyboards, even ones with USB-C, still use USB 1.1 because they don’t need the extra speed, and 1.1 cables are cheaper because the low speed allows them to be unshielded and still not suffer much interference.
Thank you!