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Black Box G.SHDSL.bis EFM CPE
4.3 TEST MODES
The LB510A-R2 offers test modes in the form of loopbacks, prbs pattern generators,
and combinations of both. This section discusses how the test modes work.
Figure 6 is a block diagram of the LB510A-R2 with respect to test modes.
Figure 7.
LB510A-R2 block diagram
4.3.1 Loopbacks
The LB510A-R2 supports both Local Analog Loopbacks (LAL) and remote digital
L
oopbacks (RDL). These can be initiated by the console command dsl set loopback
<off
|lal|rdl
>
. The data path for the LAL is shown in Figure 7.
NOTE: Local loopback causes bit errors on the remote end if the link is up.
Figure 8.
Local Analog Loopback diagram
The data received is looped back before going out on the DSL line. Note that this loop-
back occurs after the pattern generator/BER meter. This means that running a 511 pat-
tern in conjunction with an LAL should result in no error detected by the meter.
The data path for the RDL is shown in Figure 10.
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