Patent ID: 7295618

Claim:
A data communication system, comprising: a transmitter unit having an transmission characteristic adjustable in accordance with equalization information, said transmitter unit being coupled to a transmission line including a pair of signal conductors to transmit a predetermined signal thereon as a pair of differential signals which simultaneously transition to different levels, said transmitter unit further including an upchannel receiver; and a receiver unit having a reception function operable to receive the predetermined signal from the transmission line and to generate equalization information by examining an eye opening of the received signal, said receiver unit including an upchannel transmitter operable to transmit an upchannel signal including the equalization information to said upchannel receiver of said transmitter unit over the transmission line and a detector operable to detect presence or absence of the predetermined signal on the transmission line, wherein said reception function is operable to be disabled, and said upchannel transmitter is operable to be enabled in response to said detector detecting absence of the predetermined signal.