Quality Monitor (QM)
When QM
Error Correction (EC)
When EC
Latching Loopback Enabled (LLEN)
When LLEN
False Loopback Immunity
ADTRAN’s Protected Loopback family of channel units include an algorithm compatible with SARTS, Hekimian, TPI, and other test systems that virtually eliminates false latching loopback occurrences. This algorithm is always enabled at 64 kbps. In addition, ADTRAN’s Protected Loopback family features a Protected Loopback mode for further false latching loopback protection.
Latching Loopback
During operation up to 56 kbps, with LLEN enabled
At 64 kbps the function of the LLEN switch is altered. At 64 kbps, placing LLEN ON will permit the IDSL
Protected Loopback
ADTRAN’s Protected Loopback supports the new proposed DDS latching loopback standard in T1E1.2/
Table 2. Protected Loopback Mode
Requirement
Loopback)
Sequence | Byte Code | # of Received | ||
Function | Bytes | |||
|
| |||
Exit data | Idle - 11111110 | Minimum of | ||
protocol |
|
| 35 Idle bytes | |
Clear existing | Transition in | Minimum of | ||
loopbacks | progress (TIP) | 35 TIP bytes | ||
| X0111010 |
|
| |
Identify device | Loopback select | Minimum of | ||
to be looped | code (LSC) | 35 LSC bytes | ||
| X0000101 | - DS0 |
| |
| X1010101 | - OCU |
| |
| X0110001 | - CSU |
| |
Prepare to loop; | Loopback |
| Minimum of | |
send MAP code | enabled (LBE) | 100 LBE bytes | ||
after 30 bytes | X1010110 |
|
| |
Activate | Minimum of | |||
loopback | (FEV) |
| 32 FEV bytes | |
| X1011010 |
|
|
Minimum of 35 TIP bytes required to disable established latching loopback.
X = Don't care bit
3. INSTALLATION
C A U T I O N !
SUBJECT TO ELECTROSTATIC DAMAGE
OR DECREASE IN RELIABILITY.
HANDLING PRECAUTIONS REQUIRED.
After unpacking the unit, inspect it for damage. If damage is noted, file a claim with the carrier, then contact ADTRAN. See Warranty and Customer Service.
WARNING
•Never install telephone wiring during a lightning storm.
•Never install telephone jacks in wet locations unless the jack is specifically designed for wet locations.
•Never touch uninsulated telephone wires or terminals unless the telephone line has been disconnected at the network interface.
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