
Installation and Operation Manual Chapter 4 Troubleshooting and Diagnostics
ASM-40 Ver. 1.0 V.54 Loopback Tests 4-3
Local
DTE
Remote
DTE
Link
Interface
Link
Interface
Transmit
REM
Pressed
Receive
Receive
Local ASM-40 Remote ASM-40
Transmit
Data
Data
Clock
Clock
Figure 4-2. Remote Digital Loopback
To activate the remote digital loopback:
1. Press the REM pushbutton on the local ASM-40 front panel.
The following LEDs are ON:
Local unit: TEST, DCD, RTS, TD and RD
Remote unit: TD, RTS, and TEST.
2. Perform the BERT test as explained above for the local analog loopback test.
If an error occurs, while the local analog loopback test described above, was
successful for both the local and remote modems, the line or the line circuits
of the local or the remote unit are not operating properly.
3. After completing the test or correcting the fault, press REM pushbutton again
to restore it to the Off position.
Local Digital Loopback (DIG)
The local digital loopback (DIG) test allows the operator at the remote end to
check the performance of the local and remote ASM-40 units, and their
connecting lines. The DIG test loops the received data back to the remote ASM-
40 (see
Figure 4-3
). The local digital loopback test is equivalent to activating the
remote loopback from the remote ASM-40.
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