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connected, an internally generated 2074 test pattern is
used. When initiating loopbacks from the U-BR1TE
craft interface, the downstream direction is
automatically selected based on the card position in the
network.
Point-to-Point Test (CRTX, LPTX)
A point-to-point (straight-away) test can be initiated via
the local craft interface toward either the U-interface
or the T1 carrier interface. In both cases, either the
internal 2047 test pattern generator or a DS0 digital test
set is used to verify the performance of the selected
bearer channel.
Local Loopback (LPBK)
A bilateral loopback can be initiated from the local craft
interface for either bearer channel. A local test pattern
source is not required for this test.
Leased Mode Testing (B1, B2, and 2B)
For leased mode applications, the D channel is typically
disabled on the U-BR1TE. Without the D channel,
standard ISDN loopbacks by way of the EOC are not
available across the T1 carrier system. For this
situation the ADTRAN U-BR1TE responds to
independent network-issued OCU and CSU latching
loopback sequences for B1 and B2, when configured as
Adjacent-to-Customer. Upon receipt of an OCU
Latching loopback sequence, the U-BR1TE initiates a
bilateral loopback for the B Channel under test. Upon
receipt of a CSU Latching loopback sequence, and
provided the U-Interface is terminated by an NT1/TA,
the U-BR1TE will issue an EOC NT1 Loopback for
the appropriate B channel. In both testsof the OCU and
CSU loopbacks, the other B Channel is not affected.
The U-BR1TE will support simultaneously testing of
both B Channels. The OCU and CSU latching
loopbacks are enabled by the following:
1. Minimum of 35 transition in progress (TIP) bytes
(*0111010).
2. Minimum of 35 LSC bytes: OCU (*1010101),
CSU (*0110001).
3. Minimum of 100 loopback enable (LBE) bytes
(*1010110).
4. Minimum of 32 far-end voice (FEV) bytes
(*1011010).
* Denotes Don't Care bit - either a 1 or a 0.
8
Upon receipt of an OCU Latching Loopback, the
U-BR1TE will provide a bilateral loopback on the
Bearer channel that received the loopback sequence.
The other Bearer channel is not affected during this
loopback.
Upon receipt of a CSU latching loopback sequence in
either B1 or B2 channels and the U-interface is in sync,
the U-BR1TE will issue an EOC loopback request to
the NT1 for the appropriate channel. If the U-interface
is not in sync, the U-BR1TE sends abnormal station
(*0011110) in both B1 and B2 channels.
For a U-BR1TE in a CSU latching loopback, receipt of
the 35 TIPs will release the test in progress, following
the release code to a U-BR1TE in a CSU test, the
U-BR1TE will issue a Return-to-Normal EOC message
to the NT1/TA.
The valid front panel tests in leased modes are ADR1,
CRTX, LPTX, and LPBK for all circuit positions.
NT1, ADR1-ADR6 loopback tests are valid for the
Adjacent-to-Customer circuit position only. ADR2
would be used to test an ADTRAN U-Repeater
deployed from the U-BR1TE.
4. MLT 3.0/ISDN CHANNEL TEST
The ADTRAN Total Access 750/1500 U-BR1TE,
P/N 1180020L1, line card is compatible with
Mechanized Loop Testing (MLT 3.0/ISDN) according
to TR-NWT-000397, Issue 3, December 1993.
Channel Test (LUNT Mode)
When the Test Initiate Voltage (116 VDC behind 8 kΩ)
is applied to the tip with the ring open of a Total
Access 750/850/1500 U-BR1TE installed in a Total
Access 1500 shelf (the Total Access 750 does not
support MLT), and configured as a LUNT, the
following events occur:
• The channel unit sends a Channel Test MP-EOC
message downstream to the LULT, signaling the
request for a MLT channel test.
• The channel unit notifies the SCU that a MLT test
is underway.
• The unit sends a 333.3 Hz tone between the tip
and ring leads. This tone is compliant with
TR-TSY-000465.
61180020L1-5, Issue 2
61180020L1-5B
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