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Alarm Definitions
Network Low Average Density
A Network Low Average Density (Network LAD) alarm event occurs when 8(N+1)Restrict is the
configured selection for Ones Density and the DSU has to insert ones in the signal it transmits
toward the network. The DSU inserts ones when channel data results in fewer ones than are re-
quired fewer by the Ones Density option.
The Network LAD alarm is only valid when the 8(N+1)Restrict option is selected for Ones Den-
sity in the DSU configuration.
Timing Loss
A Timing Loss (Timing Loss) alarm event occurs when the DSU loses its configured timing source.
The DSU uses its timing source to supply transmit timing for the network interface and the cascade
interface when it is installed, and to supply both transmit and receive timing for channel data.
Channel Alarms
DCD Loss
A Data Carrier Detect (DCD) Loss alarm event occurs when the DSU cannot recover data from the
incoming signal at the network interface.
DSR Loss
A Data Set Ready (DSR) Loss alarm event occurs when the DSU is not outputting Data Set Ready
to the DTE.
DTR Loss
A Data Terminal Ready (DTR) Loss alarm event occurs when the DSU is not receiving the DTR
signal from its DTE.
External Transmit Timing Loss
An External Transmit Timing Loss alarm event occurs when the DSU, configured for external
timing, stops receiving the transmit clock signal from its DTE.
Receive Data No Transitions
A Receive Data (RxD) No Transitions alarm event occurs when Receive Data being output to the
DTE by the DSU consists of all ones or all zeros.
Transmit Data No Transitions
A Transmit Data (TxD) No Transitions alarm event occurs when Transmit Data coming to the DSU
from the DTE consists of all ones or all zeros.
Other Alarms
EEPROM Checksum Error
An EEPROM Checksum alarm indicates that the DSU has computed a checksum for its software
configuration that does not match the one it stored when it was configured. The DSU continually
tests for this condition.
076R155-000
Issue 7
SpectraComm 553 Fractional T1 DSU
Installation and Operation Manual
Channel Alarms
C-3
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