Functions of LEDs are as follows:
Fiber
The green Fiber LED indicates reliable data on the fiber side
E1
The green E1 LED indicates reliable data on the G.703/G.704
side
LOS
The red LOS indicates that syncronization between modems
has not been established. Blinking red LOS LED indicates the
presense of coding errors
NS
The red NS LED indicates that the signal on the fiber side is
too weak to be detected, which can be due to any of the fol-
lowing reasons:
- break in the fiber optic cable
- length of the fiber optic cable exceeds the maximum dis-
tance
- problem with Fiber LED.
ER
Flashing red ER LED indicates errors in 511 test pattern
TM
The yellow TM LED indicates that modem is in a test mode
(Local/Remote Loopback or 511/511E test pattern). Opaque
TM indicates normal operation.
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5.3 TEST MODES
The following section describes the test patterns and loopbacks
used in the Model 1186. The Model 1186 offers V.54 compliant
local/remote loopback tests, plus a built-in V.52 BER test pattern gener-
ator to evaluate the condition of the modems and the communication
link. These tests can be activated physically from the front panel.
5.3.1 Local Loopback
The local loopback test checks the operation of the local Model
1186, and is performed separately on each unit. The following section
describes how to perform a local loopback test between the Network
and a local connection.
Any data sent to the local Model 1186 in this test mode will be echoed
(returned) back to the user (see Figure 11). If two Model 1186 units are
linked when the LAL is activated, data sent from the remote modem will
also be looped back to the remote terminal equipment.
To test the local connection, follow these steps:
1. Activate LAL by moving the front panel toggle switch UP to "Local".
Once the Local Loopback is activated, the Model 1186 transmit output
will be connected to its own receiver. The TM LED will light up.
2. Perform a BER (Bit Error Rate) test on each unit using a separate
BER tester. If the BER test equipment indicates no faults, but the data
indicates a fault, follow the manufacturer's checkout procedures for the
data terminal. Also, check the interface cable between the terminal and
the Model 1186. The BER test can also be performed using a built-in
511/511E pattern generator. (See section 5.3.3 on how to use the built-in
511/511E pattern generator.)
3. Upon completion of the LAL test, return the front panel switch to the
NORMAL position. The TM LED should turn off.
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Figure 11.
Local Loopback Diagram
G.703/G.704
Network