In a departure from both 10BASE-T and 100BASE-TX,
1000BASE-T and faster use all four cable pairs for simultaneous transmission in both directions through the use of
telephone hybrid-like signal handling. For this reason, there are no dedicated transmit and receive pairs. 1000BASE-T and faster require either a straight or one of the crossover variants only for the autonegotiation phase. The physical medium attachment (PMA) sublayer provides identification of each pair and usually continues to work even over cable where the pairs are unusually swapped or crossed.