Test From the Front Panel

Push and release the test switch. All front panel light emitting diode (LED) status indicators turn red for two seconds. After two seconds, the LRU STATUS turns green and the other LEDs remain red. Then all the LEDs go off for two seconds. At this time, the applicable LEDs come on to show the condition of the ATC transponder system. After 30 seconds, all LEDs go off. These are the LED status indicators and their related conditions:

· LRU STATUS (GREEN) - no LRU failures

· LRU STATUS (RED) - LRU failure

· ANTENNA TOP FAIL - top antenna fails

· ANTENNA BOT FAIL - bottom antenna fails

· ALTITUDE FAIL - altitude input from the ADIRU fails

· CONTROL FAIL - control panel input fails.