0049-2702-XXX Alliance Series Modems – USER MANUAL
08/05/2010
Rev. A
Page 147 of 197
Figure 6-3. External analog loopback (ALBX) test
IMPORTANT:
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.
To run this test, follow these steps:
Make sure the local modem is not in communication with the remote modem, 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 TIA/EIA
status screen, the DTR circuit is on.)
From screen 2 of the LCD MAIN MENU, select TEST. Go to screen 2 of the LOCAL TEST
menu and select ALBX.
The ANALOG LOOP (EXT) 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
2 should be left ON – the default selection – to avoid disrupting the DTE and DTE software
operations.)