MLT (Multi-Level Transition) A technique used in 100Base-TX Ethernet to reduce the signaling rate and thereby lower the carrier frequency in consideration of attenuation issues over twisted pair cable.The line coding technique used in 100Base-TX is 4B/5B, which increases the signaling rate to 125 Mbps in support of a datastream of 100 Mbps. MLT-3 is a ternary approach that cycles through three signal levels in the pattern +V, 0V, –V and adds a scrambling step before placing the signal on the line (see Figure M-2). In combination, these intermediate steps support a signaling rate of 125 Mbps while placing the main spectral energy at a frequency of only 31.25 MHz. That low frequency results in improved signal quality and 74570c13.qxd 9/11/07 12:25 PM Page 313 |