Self-Test; Loopback Tests; Figure 1-5. Network Loopback Tests - ADTRAN TSU LT User Manual

TSU LT User Manual

Self-test

The self-test checks the integrity of the internal operation of the electronic components by performing
memory tests and by sending and verifying data test patterns through all internal interfaces. Although
actual user data cannot be passed during these tests, the self-test can run with the network and DTE
interfaces in place and without disturbing any external interface.
The self-test automatically executes upon power up. It can also be commanded from a front panel menu or
from the control port.
In addition to the specified self-tests, background tests are also run on various parts of the internal
electronics. These run during normal operation to confirm continued correct functioning. The background
tests include:
• Monitoring the phase-locked loop for lock.
• Standard background network performance monitoring, as required by ANSI T1.403 and AT&T 54016
for which the results are stored.

Loopback Tests

A number of different loopbacks can be invoked locally from the front panel, by T-Watch commands, or
remotely by using special inband codes. These include AT&T D4 network loop up/loop down codes and
V.54 loop up/loop down codes for the Nx56K/64K serial interface. Additionally the loopbacks can be
remotely controlled by out-of-band commands via the T1 ESF facility data link (FDL), or from T-Watch
via a modem connection. Network and DTE interface loopbacks are discussed in this section.
Network Loopbacks
There are three types of network loopbacks. See Figure 1-5.
Line Loopback
Loops all of the received data back toward the network. The transmitted data is the identical line code
that was received, including any bipolar violations or framing errors.
Payload Loopback
Similar to line loopback, except that the framing is extracted from the received data and then
regenerated for the transmitted data.
Data Loopback
Loops back all active DS0s and inserts idle code into unoccupied DS0s.
61202060L4-1

Figure 1-5. Network Loopback Tests

© 2002 ADTRAN, Inc.
Chapter 1. Introduction
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