In uk.d-i-y, bweebar wrote:

The T568B configuration is what you end up with on the second RJ45 if
you wire the first in the T568A configuration in a crossover cable.

Yup - at least for the "important" two pairs (1-2 and 3-6). The Web has
contradictory claims on how the usually-unused pairs (4-5 and 7-8) should
be wired for a general-porpoise crossover cable - most diagrams suggest
wiring these two straight-thru, but a vocal minority suggests the other.
Makes b-all difference in normal use, since (a) only a small fraction of
deployed structured wiring makes use of these other pairs, and (b) of
those, the great majority will use a "real" device to which all nodes
link (hub/bridge) - which increasingly do autodetect of which pins are
presenting R+/R- to entirely eliminate the need for crossover cables at
all...

Stefek