Black Box 32144, Manual

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150
MODEM 32144
NOTE
The ALXST 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
ALXST includes all
impairments of both the
inbound and out-bound
channels (amplitude distor-
tion, delay distortion, noise,
etc.). The main purpose of
the ALXST 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.
TRANSMITTER
PATTERN
GENERATOR
RECEIVER
PATTERN
DETECTOR
EXTERNAL LOOPBACK
(LEASED LINE)
Fig. 7-4. External Analog Loopback Self Test (ALXST).