Specifications

In-band Loopbacks
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IN-BAND LOOPBACKS
Along with the LBK pushbutton on the front panel, loopbacks are activated or de-activated
with TL1 or in-band commands.
Activating Loopbacks
The repeater circuit can be activated from either the DSX or CPE side of the T1-OR/NIU.
When activated from the DSX side, all components, including line-side transformers, are
tested. When activated from the CPE side, only the active components of the repeater are
tested. Loopbacks can only be active on one interface at a time using in-band codes. Loopback
codes are shown in Table 9.
Code Detection
The T1-OR/NIU is capable of detecting loopback codes from either direction, network or
customer. Direction determination is accomplished with the application of an arming code. By
sensing the arming code for at least five seconds on one side of the T1-OR/NIU, the code
direction is determined and the loopback is activated.
NOTE
All in-band codes must be detected for more than five seconds.
MAINTENANCE
The T1-OR/NIU does not require routine maintenance for normal operation. Do not attempt
repairs in the field. Obtain repair services by returning the defective unit to ADTRAN. Refer to
“Appendix B, Warranty” for further information.
Table 9. Loopback Codes
Code Description
In-band Loopback
Arming/Disarming Codes
Arming: 11000
Disarming: 11100
Loopback Activation Code:
1101 0011 1101 011
Acknowledgement is 250 bit errors
(bit errors are inserted after initial 6 seconds and in 20
second intervals thereafter)
Loop Down Code:
1001 0011 1001 0011
(Unit returns to the Armed State.)
Arming Timeout: 120 minutes
Loopback Timeout:
Provisionable for 30 minutes (default), 120 minutes, or No
Note: To be acted on, these codes must be detected for more than five seconds.