Notes:
From Ethernet - The Definitive Guide
1000BaseT uses a complex block-encoding scheme called 4D-PAM5 (4 data lines, 5 level PAM encoded) 0 to plus/minus 1 VDC (diferential) on the wire, 125 M Baud on each of 4 data pairs (2 bits/baud). 1000BaseT also encludes error correcting codes (ECC) in the data encoding. These modulation and encoding techniques were first used in the 100BaseT2 standard (not very widely implemented).
1000BaseT physical implementations (PHY) require sophisticated digital signal processing (DSP) to perform Near-End Crosstalk (NEXT), Far-End Crosstalk (FEXT), and signal equalization to compensate for distortion from the UTP wiring.
During autonegotiation, one end of the 1000BaseT connection will be elected master clock, the other end will be the slave clock. As with the 100BaseT/F standard, the cable is always active. IDLE signals are sent if no data is present
1000BaseT uses all eight wires in a TIA-465 eight position RJ-45 connector (10/100BaseT only used four).