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6.3 The Modem Self-Test
To verify that the line driver itself is operating correctly, initiate the modem self-
test by pressing the PATT and ANA buttons (refer to Figure 6-3 below):
1. Press ANA to start local analog loopback. Both the TEST and DCD LEDs
should light. If the DCD LED doesn’t light, make sure that the RTS signal is
not OFF (low) while the CARRIER jumper is OFF.
2. Press PATT to begin test-pattern transmission. Verify that the TEST and DCD
LEDs are still lit and that the ERR LED lights briefly.
3. If the ERR stays lit or continues to flicker after the initial flash, the line driver
is faulty; call Black Box to arrange for repair or replacement. Otherwise, the
unit passes the test; restore all of the buttons to their normal positions.
Figure 6-3. Modem self-test.
6.4 Local Analog Loopback
Activate the local analog loopback test by pressing the ANA button or by raising
the level of the Local Loopback signal received by the line driver’s V.35 connector
(Pin JJ). This test checks the performance of the local line driver, the local DTE,
and the connections between them. Perform this test separately at the local and
remote sites (refer to Figure 6-4 on the next page):
1. Press ANA or raise Local Loopback to start local analog loopback. The
TEST LED should light. The line driver’s G.703 transmit output should be
connected to its own receiver.
PATTERN
GENERATOR
PATTERN
TESTER
ERROR
PATT
DEPRESSED
ANA
DEPRESSED
XMTR
RCVR
CHAPTER 6: Troubleshooting