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In Hayes emulation mode only,
the ALB test can be initiated using
the command &T1 (preceded by
AT). In any mode, the ALB test can
be initiated by using the modem's
front panel controls, as explained
in the following paragraphs.
Make sure the modem is idle,
that the data rate is the same as
that of the DTE and that the DTR
circuit is on. (If TR is present on
the EIA status screen, the DTR
circuit is on.)
From screen 2 of the LCD MAIN
MENU, select TEST. This will take
you to screen 1 of the LOCAL
TEST menu, where ALB will be
displayed as one of the test
selections. Select ALB.
The ANALOG LOOPBACK
screen will be displayed, with ON
and OFF as the possible selections.
Select ON to activate the test. (In
general, the DSR during ALB test
option discussed in chapter should
be left ON—the default selection—
to avoid disrupting the DTE and
DTE software operations.)
CHAPTER 7: Diagnostics
The EIA status screen will be
displayed while the test is being
conducted. Ensure that test data
is being generated. Watch for data
errors. By transmitting test data
and comparing it with the received
copy, the DTE and modem are
checked for proper operation.
To end the test, press the ENT
pushbutton to return to the
ANALOG LOOPBACK screen,
and then select OFF.
7.8.2 A
L
NALOG
OOPBACK
(ALBST)
In the analog loopback self-test,
the modem is placed in analog
loopback and data is sent and
received by an internal 511-bit
pattern generator and receiver;
therefore, no DTE or external
BERT is necessary. Fig. 7-2 shows
the data flow for this test.
S
-T
ELF
EST
145
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