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MICRONTU G.703 CARD (120 OR 75 OHM)
Power
Glows red when the Card is powered up.
Network
Glows green when the Card is receiving correctly
encoded data from the line-interface equipment.
Master Clock
Glows green when the Card is configured as the master
clock unit.
Loop
Glows green when the Card is in loopback mode.
5.3 Loopback Test (LAL)
The MicroNTU G.703 Card is equipped with a Local Analog Loopback (LAL)
mode to assist in evaluating the operation of the local MicroNTU G.703 Card.
Any data sent to the local MicroNTU G.703 Card in this test mode will be
echoed back (returned) to the user device. For example, characters typed on
the keyboard of a terminal will appear on the terminal screen. To perform a
LAL test:
a.) Activate LAL by moving the front-panel toggle switch up and holding it
in the “Loopback” mode. The “Loop” LED should glow. Once LAL is
activated, the MicroNTU G.703 Card transmit output is connected to
its own receiver.
NOTE
The front-panel switch is spring loaded, so it will return to “Normal”
operating mode when pressure is released.
b.) Verify that the data-terminal equipment is operating properly and can
be used for a test. If a fault is indicated, call Black Box for technical
support or replace the unit.
c.) Perform a BER (bit error rate) test on each unit. If the BER test
equipment indicates no faults, but the data terminal indicates a fault,
follow the manufacturer’s checkout procedures for the data terminal.
Also, check the interface cable between the terminal and the
MicroNTU G.703 Card.
