Ittennéka konjugálsz, de lusta vagy olvasni. :)
Itt a link tartalma:
The cable length was limited by a cable delay spec of 26ns to allow for reflections to settle at the transmitter before the next bit was sent. Since USB uses source termination and voltage-mode drivers, this has to be the case, otherwise reflections can pile up and blow the driver. This does not mean the line voltage has fully settled by the end of the bit; with worst-case undertermination. However, there's been enough damping by the end of the bit that the reflection amplitude has been reduced to manageable levels. The low speed cable length was limited to 18ns to keep transmission line effects from impacting low speed signals.
Mindez "szabad műfordításban" annyit tesz, hogy lezáratlan a kábel, és ha a bit időt eléri a késleltetés, akkor rossz esetben elfüstöl az adó a visszaverődés miatt. Hát ezért az 5m maximális hossz, mert az pont egy bit. ;)