4 61433105L2-5DSection 61433105L2, Issue 4
Figure 4. DS0 Bidirectional Loopback
Series 5
TR
DDS-DP
DS0
Bidirectional
loopback
Customer
Intra-office
DS0 DP units. The Total Reach DDS-DP only responds
to latching DS0 DP loopback sequences.
NOTE
If 64 kbps is selected, the unit will only respond
to latching loopback sequences. Alternating
sequences are not valid at this rate.
Total Reach DDS-DP Bidirectional Loopback
Support
The Series 5 Total Reach DDS-DP will execute a
bidirectional loopback when performing a DS0 loopback,
as shown in Figure 4. This allows a standard portable
DDS test set, connected to the 4-wire customer
interface of the Total Reach DDS-R, to verify the integrity
of the 2-wire loop by transmitting a test pattern and
examining the returning data for synchronization and
errors. The Series 5 Total Reach DDS-DP LBK
indicator will illuminate during this test mode.
The Series 5 Total Reach DDS-DP also responds to a
loopback command sent by the Total Reach DDS-R
when the LBK button on the Total Reach DDR-R is
pressed. This allows loop testing to be performed from
the remote end without test center coordination. The
SLC Series 5 Total Reach DDS-DP only performs a
loopback towards the customer in this case. The latching
and alternating loopback sequences are defined in Table
3 and Table 4.
Total Reach DDS Trouble Code
The Total Reach DDS system is designed to provide a
quick diagnosis in the case of a circuit condition
where continuity is broken. The trouble code type
received by a tester determines whether the open
condition is occurring on the local loop or at the
customer premises. In the event of an open conductor
or disconnected 2-wire loop, the Total Reach DDS-DP
transmits an alternating ASC/MOS trouble code into
the network as shown in Figure 5. In the event of a
4-wire open or disconnect, the TR DDS-R sends an
ASC to the network as seen in Figure 5.
Remote End Initiated LBK Tests
The Total Reach DDS-DP supports loopbacks
generated from the TROCU-R which allow testing to
be performed without coordination with the CO or test
center. Loopbacks initiated by the TROCU-R front
panel LBK pushbutton aid in system turn-up testing or
troubleshooting from the remote end.
Table 2. LED Indication
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