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Options
Select the appropriate Option and Rate using circuit board switches SW1 and SW4 as illustrated in
Figure 2. Select options prior to board insertion.
Protected Loopback (PLB)
ADTRAN's Protected Loopback supports the new proposed DDS latching loopback standard
in T1E1.2/99‐007R1. When Protected Loopback is enabled, the TR DDS‐DP will respond to
latching loopback when the idle code preamble is sent prior to the latching loopback sequence
specified in TR62310 and ANSI T1.107.
Protected Loopback prevents false latching loopbacks when the loopback sequence is
embedded in customer payload data. Test equipment should support T1E1.2/99‐007R1 to
perform testing at 64 kbps when protected loopback is enabled.
See Table 6 for the latching loopback sequence requirement when Protected Loopback is
enabled.
Exit Data Protocol
Clear existing loopbacks
Identify device to be looped
Prepare to loop; send MAP code
after 30 bytes
Activate loopback
61180105L1-5C
1
1
1
2
2
2
3
3
3
O
O
O
N
N
N
Figure 2. Option and Rate Selection Switches
Table 6. Protected Loopback Mode Requirement
Sequence Function
4
4
4
5
5
5
1
1
1
2
2
2
3
3
3
4
4
4
5
5
5
O
O
O
N
N
N
Byte Code
Idle ‐ 11111110
Transition in
progress (TIP)
X0111010
Loopback select code (LSC)
X0000101 ‐ DS0
X1010101 ‐ OCU
X0110001 ‐ CSU
X1000001 ‐ NIE
Loopback enabled (LBE)
X1010110
Far‐End voice (FEV)
X1011010
Provisioning
6
6
6
7
7
7
8
8
8
# of Received Bytes
Minimum of 35 Idle bytes
Minimum of 35 TIP bytes
Minimum of 35 LSC bytes
Minimum of 100 LBE bytes
Minimum of 32 FEV bytes
9
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