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Chapter 1. Introduction
TSU 120 TESTING
Self Tests
Loopback Tests
1 6
The TSU 120 offers three forms of testing:
• Self test
• Loopback tests (local and remote)
• Pattern generation and check
The self test checks the integrity of the internal opera-
tion 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 be run with the network and DTE
interfaces in place and will not disturb any external
interface.
The memory portion of the self test automatically
executes upon power up. A full self test can be
commanded from a front panel menu or from T-
Watch.
In addition to the specified self tests, background tests
are also run on various parts of the internal electron-
ics. These run during normal operation to confirm
continued correct functioning. The background tests
include:
• Monitoring the phase locked loop for lock
• Sending test data through a parallel path which is
looped back and verified
• The standard background network performance
monitoring, as required by ANSI T1.403 and AT&T
54016 specifications for which the results are stored
A number of different loopbacks can be invoked
locally from the front panel, by T-Watch commands, or
remotely by using special in-band codes (AT&T D4
network loop up and loop down codes; V.54 loop up/
loop down codes for the Nx56/64 serial interface).
TSU 120 User Manual
61200.129L1-1
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