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CHAPTER 5: Operation
5.1.2 R
EMOTE
D
IGITAL
L
OOPBACK
(RDL)
The Remote Digital Loopback (RDL) test checks the performance of both the
local and remote modems, and the communication link between them. Any
characters sent to the remote modem in this test mode will be returned to the
originating device. For example, characters typed on the keyboard of the local
terminal will appear on the local terminal screen after having been passed to the
remote modem and looped back. To perform an RDL test, follow these steps:
1. Activate RDL. This may be done in two ways: First, by moving the front-panel
toggle switch up to RDL. Second, by raising pin 21 on the interface.
NOTE
Make sure SW1-8 is OFF.
2. Perform a BER (bit error rate) test on the system.
3. If the BER test equipment indicates a fault, and the Local Analog Loopback
test was successful for both modems, you may have a problem with the twisted-
pair line between the modems. You should then check the fiber line for
proper connections and continuity.
5.1.3 U
SING THE
V.52 BER T
EST
I
NDEPENDENTLY
The V.52 BER test can be used independently of the V.54 loopback tests. This
requires two operators: one to initiate and monitor the test at the local modem,
and one at the remote modem. To use the V.52 BER test by itself, both operators
should simultaneously follow these steps:
1. Locate the 511/511E toggle switch on the front panel of the modem and
move it DOWN. This activates the V.52 BER test mode and transmits a 511
test pattern to the other unit. If any errors are present, the receiving modem’s
red Error LED will blink sporadically.
NOTE
For this test to function, the 511 switch on both modems must be on.
2. If the test indicates no errors are present, move the V.52 toggle switch UP,
activating the 511E test with errors present. If the test is working properly, the
receiving modem’s red Error LED will glow. A successful 511E test will
confirm that the link is in place, and that the modem’s built-in 511 generator
and detector are working properly.