7-1
7914-A2-GB20-00
February 1998
Testing
7
Detecting a Problem
The unit can detect and report problem conditions and perform diagnostic tests.
The unit offers a number of indicators to alert you to possible problems, as
described in Chapter 6,
Monitoring the Unit
:
Board Status and performance statistics
Remote unit board status and performance statistics
Front Panel LEDs
Understanding Loopback Tests
Loopback is a diagnostic function that enables a technician to isolate equipment
on the SDSL circuit to determine where on the circuit trouble may be occurring.
Loopback takes the system off-line. Data received from T1 or V.35/V.11
application equipment is looped back.
“Local” and “remote” refer to the point at which the data is looped back. In a local
loopback the data is reflected back by the local unit (the unit that initiated the
loopback). In a remote loopback, the data is passed on to the remote (far-end)
unit and then reflected back.
Figures 7-1
through 7-4 illustrate how local and remote loopbacks operate in
different configurations. The bold arrows indicate the direction of data flow.
