User's Manual

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126
The presence of the loopback should be seen at the BER test set. Inject 1 error into
the test signal and observe it on the incoming signal to check that errors are detected.
Start and stop the test to clear the injected error.
Observe the return signal on the T1/E1 out to establish that the link is error free. Run
BER test for 1 Hour.
On completion of the test remove the loopback (open the Edit DA ST window and click
the Loopback box to remove the tick and click OK.)
Delete CAS subscriber in Sitespan, and delete CAS XTU.
b) Testing at the Subscriber Terminal if L Series SIU used.
An alternative method of testing the BER of a link from a CT to an ST is to provide a
hard wired loopback on a selected E1/T1 port on a Data XTU Card at the AC site. By
using an ST-L128 or ST-l64, 128kbit/s or 64kbit/s data rates may be tested using a
BER tester at the ST location. The advantage of this method is that there is no need to
have a person at both the AC site and the ST test location
Note. A suitable data cable from the BER test set is required. Most BER test sets
provide V.35 or X.21 synchronous interface options.
Power for a prolonged test may be a problem in field locations . An inverter running
from a vehicle 12V supply may be used for tests of up to 1 hour with the ST powered
directly from the Vehicle battery Place a physical loop on the E1/T1 at the
AC/Exchange.
At the AC site: Loopback E1 link on Data XTU card. (loop on shelf backplane or DDF)
At the Subscriber Terminal: Connect BER test set to the ST.
The presence of the loopback should be seen at the BER test set. Inject 1 error into
the test signal and observe it on the incoming signal to check that errors are detected.
Start and stop the test to clear the injected error.
Observe the return signal on the E1/T1 out to establish that the link is error free. Run
BER test for 1 Hour.
On completion of the test remove the loopback and re-connect the E1/T1.
Delete test data subscriber in Netspan.