Signal Label Mismatch. A SONET port status indicator that activates when an SLM defect occurs and does not clear throughout the alarm integration period, which is typically 2.5 seconds. An SLM defect occurs when the received path signal label is not set for either the Equipped-Non Specific (0x01) or ATM (0x13) code for five consecutive samples within a 250 ms window. This occurrence begins the alarm integration period. If this period elapses without detecting a valid code (that is, 0x01 or 0x13) for five consecutive samples within a 250 ms window, the SLM indicator activates. The SLM indicator clears when an SLM defect does not occur for a time interval equal to the alarm deactivation period (typically 10 seconds).