When you wire one end of a cable with T568A and the other end with T568B, you create a crossover cable. In a crossover cable, the transmit (TX) wires on one end are connected to the receive (RX) wires on the other end.

Here's a breakdown of the wire pairings:

* T568A:

* Green-White: TX+

* Green: TX-

* Orange-White: RX+

* Orange: RX-

* Blue-White: Unused

* Blue: Unused

* Brown-White: Unused

* Brown: Unused

* T568B:

* Orange-White: TX+

* Orange: TX-

* Green-White: RX+

* Green: RX-

* Blue-White: Unused

* Blue: Unused

* Brown-White: Unused

* Brown: Unused

Essentially, the green and orange pairs are swapped between the two ends of the cable.

This wiring scheme is used to directly connect two network devices that would normally require a hub or switch. For example, you can connect two computers directly using a crossover cable without needing a network hub.

However, with the prevalence of auto-MDIX (automatic Medium Dependent Interface crossover) in modern network devices, crossover cables are less common. Most devices can detect the cable type and automatically adjust for proper communication.