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Modem 34336
Figure 7-2. Analog Loopback Self-Test (ALBST).
The SELFTEST screen is displayed, with ON and OFF as the possible
selections. Select ON to activate the test. The EIA status screen is displayed
while the test is being conducted. If ER is present on the front panel, data
errors occurred. The ER indicator may flash on when the test is first started,
but it should quickly go out and remain off until the end of the test.
To end the test, press the ENT pushbutton to return to the SELFTEST screen.
Then select OFF.
7.7.3 A
NALOG
L
OOPBACK
S
ELF
T
EST
W
ITH
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. 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
7-2 (the ALBST).
External loopback
(leased line)
829 Block
Transmitter Receiver
Pattern
generator
Pattern
detector