Ericsson RBS 2106 Reference Manual page 432

Transmission Interface Handling DS1 1544 kbit/s
Two disturbance frequency counters exist. Both are derived from the
downstream PCM port, but one is closely connected to downstream
faults while the other one is related to upstream faults.
The DF downstream counter is incremented by 1 for each occurrence of
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The DF upstream counter is incremented by 1 for each occurrence of
RAI.
Every detected fault situation is registered and regarded as a disturbance,
even if it does not last long enough to be recognised as a fault.
The DF is supervised and reported as the number of disturbances during
the BI. Both counters are handled separately.
Slip Frequency supervision
This supervision monitors the number of slips per time interval. A slip
is defined as where one frame (193 bits) is either lost or duplicated.
The SF counter is incremented by one for each slip on the PCM port
upstream or on the PCM port downstream.
The SF is supervised and reported as the number of slips during the BI.
Errored Seconds supervision
An ES is a second with at least one of the following events:
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Two counters for errored seconds exist. Both are derived from the
downstream PCM port, but one is closely connected to downstream
faults while the other one is related to upstream faults.
The downstream counter is incremented by 1 for each second with at
least one of the events:
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The upstream counter is incremented by 1 for each second with at least
one
430 (485)
LOF or
LOS or
AIS
CRC-6 error
LOF alignment
LOS
Slip
AIS
RAI
CRC-6 error or
LOF or
LOS or
AIS or
Slip
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EN/LZT 720 0008 P2A
2001-11-28