42
LDM-MR19.2
Figure 6-1. A local LDM-MR19.2 in analog loopback.
6.1.2 C
OMMUNICATION
-L
INK
T
ESTS
: D
IGITAL
L
OOPBACK
6.1.2.A Remote Digital Loopback
Use the Remote Digital Loopback test to check the performance of both the local
and the remote LDM-MR19.2 and the lines between them (see Figure 6-2 on the
next page). Take these steps:
1. Press the REM (Remote Loopback) pushbutton on the front panel of the unit
you want to test. The TEST LED should light. Pressing the local unit’s REM
button causes a loopback at the remote LDM-MR19.2.
2. Perform a terminal test or BERT (see
Section 6.1.1
).
3. If Step 2 indicates a fault, and if the modem test described in
Section 6.1.1
was successful for both modems, the telephone-line circuits
are not operating properly.
6.1.2.B Local Digital Loopback
To activate this test, press the DIG pushbutton. Pressing the local unit’s DIG
button causes it to loop the received data back to the remote unit (see Figure 6-3
on the next page). The operator at the remote end can check the performance of
both the local and remote LDM-MR19.2s and the telephone lines between them.
DATA
TERMINA
XMTR
RCVR
DAT
CL
CL
DAT
LIN
ALB
PRESSED
