DTR
Glows green to indicate that the Data Terminal
Ready signal from the terminal is active.
ER
Glows red to indicate the likelihood of a Bit Error in
the received signal. .
TM
Glows red to indicate that the Model 2530 has
been placed in Test Mode. The unit can be placed in
test mode by the local or remote user.
NS
Glows red to indicate that the local Model 2530 has
not yet connected with the C.O. (or to the remote
Model 2530 when used in campus short haul
application).
5.3 LOOP (V.54 & TELCO) DIAGNOSTICS
The Model 2530 offers three V.54 loop diagnostics and is compati-
ble with two Telco loop diagnostics. Use these diagnostics to test the
CSU/DSU and any communication links. These tests can be activated
physically from the front panel, or via signals on the
QuikConnect™
interface.
5.3.1 Operating Local Analog Loopback (LAL)
The Local Line Loopback (LAL) test checks the operation of the
local Model 2530, and is performed separately on each unit. As shown
in Figure 6, below, any data sent to the local Model 2530 in this test
mode will be echoed (returned) back to the user device (i.e., characters
typed on the keyboard of a terminal will appear on the terminal
screen).
To perform a LLB test, follow these steps:
1.
Activate LAL. This may be done in one of two ways:
a.
Move the front panel toggle switch UP to “Local”; or,
b.
Activate the “LL” signal on the DTE. If you are not sure
which lead is the “LL” signal, please refer to Appendix D.
25
2.
Verify that the data terminal equipment is operating properly
and can be used for a test.
3.
Perform a V.52 BER (bit error rate) test as described in
Section 5.3.3. If the BER test equipment indicates no faults,
but the data terminal indicates a fault, follow the manufactur-
er’s checkout procedures for the data terminal. Also, check
the interface cable between the terminal and the Model 2530.
5.3.2 Operating Remote Digital Loopback (RDL)
The Remote Digital Loopback (RDL) test checks the performance
of both the local and remote Model 2530s, as well as the communica-
tion link between them. Any characters sent to the remote Model 2530
in this test mode will be returned back to the originating device (i.e,
characters typed on the keyboard of the local terminal will appear on
the local terminal screen after having been passed to the remote
Model 2530 and looped back).
To perform an RDL test, follow these steps:
1.
Activate RDL. This may be done in two ways:
a.
Move the front panel toggle switch DOWN to “Remote”;
b.
Activate the “RL” signal on the DTE. If you are not sure
which lead is the “RL” signal, please refer to Appendix D.
2.
Perform a bit error rate test (BERT) using the internal V.52
generator (as described in Section 5.4), or using a separate
BER Tester. If the BER test indicates a fault, and the Local
Line Loopback test was successful for both Model 2530s, you
may have a problem with the twisted pair line between the
modems. You should then check the twisted pair line for prop-
er connections and continuity.
26
Figure 6. Local Line Loop
Local 2530
Figure 7. Remote Digital Loop
Local 2530
Remote 2530
