Chapter 5.Loop Back & BERT Testing
59
May 2011
E1 line remote analog loop back
E1 line remote analog loop back is performed by sending a loop back code to the remote unit.
The remote unit then connects its E1 link receive signal to the output of the transmit path, before
the Channel Service Unit (CSU). This loop back test checks the performance of the local ETU-01A,
the remote ETU-01A and the connections between them, as shown in Figured 5-4.
Figure 5-4. E1 link remote analog loop back
Note:
The remote loop back codes, also referred to as data link messages, for the ETU-01A utilize
the 4 spare Sa bits within the framing timeslot (TS0). Therefore, any remote loop back functions,
including remote analog loop back (LLB) and remote payload loop back (PLB) are only available
when running in framed mode (PCM30 or PCM31). Unframed mode does not support any remote
loop back functions.
E1 line remote payload loop back
E1 line remote payload loop back is performed by sending a loop back code to the remote unit.
The remote unit then connects its E1 link receive signal to the output of the transmit path, before
the Digital Service Unit (DSU). This loop back test checks the performance of the local ETU-01A,
the remote ETU-01A and the connections between them, as shown in Figured 5-5.
Figure 5-5. E1 link remote payload loop back
DTE
DSU
E1
CSU
LOCAL ETU-01A
DTE
DSU
CSU
REMOTE ETU-01A
DTE
DSU
E1
CSU
LOCAL ETU-01A
DTE
DSU
CSU
REMOTE ETU-01A
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