The last step is PAM3, which converts the logical -1, 0, 1 into the voltage on the twisted pair, so the final baud rate of the signal on the bus is 66.666MHz, but it achieves a communication rate of 100Mbit/s.
echo cancellation technology
10BASE-T and 100BASE-TX have two pairs of signal lines, which are respectively received and transmitted, but 100BASE-T1 is also a physical full-duplex interface, but allows transmission and reception on the same pair. This physical full duplex is accomplished through the superposition principle, the 100BASE-T1 PHY has an integrated hybrid function and uses echo cancellation to cancel its own transmit signal and extract the received information from the link partner. To do this, one PHY is dedicated as a master and the other as a slave. When two 100BASE-T1 PHYs connect, they go through a training process that causes the device under test (DUT) and link partner to transmit information at the same frequency and in the same phase. The figure below illustrates a simplified block diagram of mixing and echo cancellation within each PHY.