13
Section 61104020L4-5, Issue 3
61104020L4-5C
During a remote end initiated loopback the system
transmits ASC 9Eh toward the network, indicating an
out-of-service condition generated by the remote end,
as shown in Figures 10 and 11.
All IDSL/DDS system latching loopbacks, whether
initiated by the IDSL DCU-R craft interface, LBK
pushbutton, CO, or from a remote Test Center, can be
released by sending 35 DDS loop down TIP bytes
<X0111010> (Where X is a “don’t care” bit). All
existing latching loopbacks will also be disabled by
pressing the LBK pushbutton on the CO or remote
unit.
NOTE
The remote end test feature is only supported
when the upstream U-BR1TE is an ADTRAN
D4 or Series 5 U-BR1TE with DDS Loopback
capability. Other U-BR1TEs will ignore the
loopback command sent by pressing the IDSL
OCU-R LBK button.
IDSL/DDS Trouble Code
The IDSL/DDS system provides 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 a 2-wire DSL loss of signal, loss of sync, or
open condition caused by an open conductor or
disconnected 2-wire loop, the U-BR1TE V transmits a
MUX-Out-of-Sync trouble code (MOS 9Ah) into the
network as shown in
Figure 12
. During a similar
out-of-service condition at the customer premises, the
IDSL OCU-R transmits Abnormal Station Code
(ASC 9Eh) upstream toward the network as shown in
Figure 12.
2B Leased Mode Operation
The U-BR1TE V is deployed in 2B leased line
operation to provide DDS/Frame Relay services to
ISDN equipment. By using the 2-wire ISDN interface
for 128 kbps data rate, the U-BR1TE V Leased Mode
Operation allows pair savings over traditional DDS
deployment. DDS/Frame Relay support allows
loopback testing to be performed across the ISDN
transport system in this configuration.
The U-BR1TE V will decode DDS latching loopback
sequences coming from the carrier into
eoc
loopback
commands usable by traditional ISDN equipment. See
Figure 13
for various U-BR1TE V DDS 2B Leased
Mode arrangements. In a SLC-96 network the
U-BR1TE V units will operate in both 2B+D or 2B
mode. Both units must be in the same mode.
Loopback Operation
To enable detection of DDS latching loopbacks, the
ADTRAN U-BR1TE V must be provisioned as an
LT- like device in leased 128 kbps (2B) mode of
operation.
When B1 and B2 are enabled, data on both channels
are looped in response to a DDS latching loopback
sequence detected on channel B1. The U-BR1TE V
will respond to a DS0 latching loopback intended for
DS0 #1. Loopback commands intended for DS0 #2
and greater are re-mapped to ISDN
eoc
loopback
commands addressed to the appropriate unit.
The U-BR1TE V will map a CSU latching loopback
sequence to an ISDN eoc NT1 loopback. Figure 13
shows the DDS latching loopback commands that will
loop each unit.
NOTE
Only the B1 channel will detect the DDS
loopback sequences for activation and
deactivation of DS0 and CSU latching
loopbacks. All standard U-BR1TE units between
the ADTRAN U-BR1TE V and the NT1 device
must have the D-channel enabled in order for
loopbacks to be processed beyond the
U-BR1TE V.
Figure 12. IDSL/DDS Trouble Codes
MOS 9Ah
Channel Bank
Open 2-wire Loop
DSU
IDSL OCU-R
Customer Premises
ASC 9Eh
Channel Bank
ASC 9Eh
Open 4-Wire Customer
Interface
DSU
IDSL OCU-R
Customer Premises
U-BR1TE
IV
U-BR1TE
IV
