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4-8 CHAPTER 4: DUAL T1/PRI STATUS DISPLAYS
■Excessive CRC Error Indication (ECRCEI)
This is reported in ESF format when 32 of any 33 consecutive CRCs are in error. The status report indicates whether or not this event occurred. A counter records the number of times an event occurred since the latest counter reset.
■Out of Frame (OOF)
This is a local alarm that indicates a framing pattern for a span is lost and data cannot be extracted properly. This is also referred to as a red alarm. In both SF and ESF formats, OOF occurs when any two of four consecutive frame synchronization bits are in error.
The status indicates whether or not OOF conditions are present.
■Loss of Signal (LOS)
The received signal is missing. This occurs when 175 consecutive 0’s are detected on the span line or when the signal is lost for 150 msec or longer. The signal is recovered when the 1’s density reaches 12.5% or when four 1’s are received within a
■Remote Frame Alarm (RFA)
This indicates that an OOF condition is occurring at the remote end. The remote end sends a bit pattern indicating a remote problem. This is also referred to as a yellow alarm. The status report indicates whether or not an RFA is present.
■Alarm Indication Signal (AIS)
This indicates to the other end that a loss of the received signal is occurring (Central Office switch sends the AIS patterns).
The remote end is alive but there are problems. This is also referred to as a blue alarm. AIS occurs when a stream of 1’s is received. The status report indicates the presence of an AIS condition.
■Loop Back
This indicates whether or not a remotely or locally initiated loopback is in progress from the network.
■Time since clear
The time in days:hours:minutes:seconds since the counters were reset and the screen was last looked at.