This reports which single DS0 channel on this port is currently in far-end loopback. This is the read-only confirmation that a far-end loop request actually landed on the intended channel of this specific port, which matters because far-end loopback commands travel inband and can theoretically be misdirected or fail silently if the far-end equipment does not respond as expected. If pportDS0SwitchLpbkStart was set to 7 to request a far-end loop but this object reports channel 6, the loop-up sequence looped the wrong DS0 on the far-end equipment and the test results would need to be discarded.