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Remote Digital Loopback with Self Test &T7
After making the data connection, enter the escape sequence to return to
command mode. Entering &T7 places the remote modem in digital
loopback provided the remote operator enters &T4 to allow an RL
request. Once in RDL/TP, the local modem transmits a test pattern and
automatically verifies that the remote modem is looping the pattern back
(Figure 7-5). Enter &T to exit RDL/TP and return to command mode.
Enter the O command to return online in data mode.
Exiting RDL/TP the modem responds with a three digit value between 0
and 255 representing the number of errors which occurred during test
pattern detection. If errors occur, repeat the test several times to verify
the consistency of the problem, then use the analog loopback tests to
isolate the problem.
Figure 7-5. Local Modem Initiating Remote Digital Loopback
with Test Pattern
Test Pattern %T
In Test Pattern, transmitted data from the local DTE is blocked and
replaced by a V.52 compatible test pattern. When the modem transmits
the test pattern, it expects to receive the same pattern.
Bilateral Digital Test Enable / Disable *DG
Enable or disable bilateral test functions.
Command
*DG
*DG1
Operation
Bilateral digital loop disabled
Bilateral digital loop enabled
Modem 3600
Test Mode Operation
7-7
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