D-2
Alarm Definitions
GDC 048R154-000
Network Unavailable Signal State
A Network Unavailable Signal State (NETWORK USS) alarm event
occurs when 10 consecutive severely errored seconds occur. It ends
when the DSU has processed 10 consecutive seconds of data without
the occurrence of a severely errored second.
Network Alarm Indication Signal
A Network Alarm Indication Signal (NETWORK AIS) alarm event
occurs when the DSU receives an AIS from the network.
Network Bipolar Violations
A Network Bipolar Violation (NETWORK BPV) alarm event occurs
when the signal the DSU receives from the network does not alternate
between signal levels as required for Alternate Mark Inversion (AMI)
or Bipolar with 8 Zero Substitution (B8ZS) data encoding.
The front panel BPV indicator reflects the current status of BPV error
events.
Network Cyclic Redundancy Checksum
A Network Cyclic Redundancy Checksum (NETWORK CRCS) error
alarm event occurs when ESF framing is in use and the CRC-6 code
calculated at the receiving DSU does not match the CRC-6 code
calculated by the DSU that transmitted the signal. The DSU performs
the CRC check on each ESF frame to detect errors in the DS1 signal.
Network Received Yellow
A Network Received Yellow (NETWORK RYEL) alarm event occurs
when the DSU receives a Yellow alarm from the network.
Network Low Average Density
A Network Low Average Density (NETWORK LAD) alarm event
occurs when the 8(N+1) Ones Density Requirement is being enforced
(DSU operating mode either Unframed/AMI or Framed/AMI/Nx64k/
Consecutive) and the DSU has to insert ones in the signal it transmits
toward the network. The DSU inserts ones and declares a NETWORK
LAD alarm when the signal from the DTE at its DTE interface port
contains fewer ones than the Ones Density option requires.
