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LOCAL MUX-6
4.4 System Tests
Two system tests are available in the Local Mux-6: local loopback and remote
loopback.
Local Loopback
When performing local loopback, the data from the local transmitter is
looped back to the local receiver at the digital level, thus checking all local
digital circuitry for proper operation. This test is activated by pressing the
LLB push-button on the front panel. If the local unit is operating properly,
the yellow TEST indicator should light, and all other indicators should be
OFF.
If the local and remote units are properly connected via the main channel,
the local transmitter analog interface and both the remote analog and digital
receiver sections are checked. The yellow TEST indicator on the remote unit
should also be lit if the units are properly connected.
Remote Loopback
Remote loopback loops back data from the remote receiver to the remote
transmitter, thus checking:
• All local digital circuitry
• Both local and remote analog interfaces
• Main channel link
• Remote digital receiver section.
This test is performed by pressing the RLB push-button on the front panel.
If both local and remote units operate properly, the yellow TEST indicators
should be lit at both units and all other indicators should be OFF.
NOTE
When either the local or the remote loopback test is performed, the
following signals at the remote unit sub-channels are set to OFF
(negative voltage) condition: Received Data (Circuit 104), Clear to Send
(Circuit 106), Receive Line Signal Detector (Circuit 109)
