This PerfCounter64 counts xDSL LOSS (Loss of Signal seconds) on an Ethernet network port's DSL line in the current bin; despite the object's 'Us' naming, the source description states it measures the downstream LOS condition. An admin treats any live increment here as a serious event, since loss of signal typically means the DSL line has fully dropped sync rather than merely experiencing noise. If cmEthernetNetPortStatsXdslUsLoss starts incrementing on a port that had been stable, the admin's first check is whether the customer's modem lost power or the line was physically disturbed.