A wired communication systems, a subscriber device and a method, and more specifically related to initialization and/or update of communication parameters used for communication through the wired communication systems. An access node comprises at least one processor and memory storing instructions that when executed by the at least one processor cause a local transceiver of the access node to transmit signaling data via a subscriber line to a remote transceiver, the signaling data identifying particular symbol positions within a sequence of symbols transmitted over the subscriber line during show-time as being suitable for characterizing a direct communication channel between the local transceiver and the remote transceiver.