Black Box 32144, Manual

Page: 61 / 195

147
CHAPTER 7: Diagnostics
To end the test, press the ENT
pushbutton to return to the
SELFTEST screen, and then
select OFF.
7.8.3 A
NALOG
L
OOPBACK
S
ELF
-T
EST
WITH
E
RRORS
(ST/E)
In the analog loopback self test
with errors, data is sent and
received by an internal 511-bit
pattern generator and receiver;
therefore, no DTE or external
BERT is necessary. This test differs
from the ALBST in that errors are
injected into the data flow every
few seconds. The data flow is the
same as that shown in figure -2
(the ALBST).
To run this test, follow these
steps:
From screen 2 of the LCD MAIN
MENU, select TEST. This will take
you to screen 1 of the LOCAL
TEST menu, where ST/E will be
visible as one of the selections.
Select ST/E.
The SELFTEST W/ERROR
screen will be displayed, with ON
and OFF as the possible selections.
Select ON to activate the test. The
EIA status screen will be displayed.
The ER indicator should flash every
few seconds, indicating that the
pattern generator and detector are
working. Errors are injected every
few seconds. To end the test, press
the ENT pushbutton to return to
the SELFTEST W/ERROR screen,
and then select OFF.
7.8.4 E
XTERNAL
A
NALOG
L
OOPBACK
(ALBX) T
EST
The external analog loopback test
is available for 4-wire leased line
mode only.
The ALBX test allows the user
to test the local modem and its
associated terminal and to verify
the availability of the leased line
circuit. The test circuit does not
include the remote modem.
Fig. 7-3 shows the connections
automatically made during the
ALBX test.
NOTE
The ALBX test may result in
errors or may fail altogether
even where conditions are
satisfactory for normal
operation. This is because
the test channel presented
to the modem during the
ALBX test.includes all
impairments of both the
inbound and outbound
channels (amplitude
distortion, delay distortion,
noise, etc.). The main
purpose of the ALBX test is
to verify that the modem is
connected to the leased line
and that the leased line
circuit is complete. The test
is not meant to assess the
suitability of the leased line.