TEST PASS
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CDS BITE PAGES - DEU SELF-TEST 2

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CDS BITE PAGES - DU LOOP TEST THIS PAGE INTENTIONALLY LEFT BLANK
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CDS BITE PAGES - DU LOOP TEST General
To do the DU loop test, select line select key (LSK) 2L, DU LOOP TEST from the GROUND TEST MENU PAGE. This shows the DU LOOP TEST MENU page. The loop test checks the interface between the DEU’s, coax coupler and Dispaly units.
DU LOOP TEST MENU Page
On the DU LOOP TEST MENU page you can select two tests.
To operate the first test, select LSK 2L. This makes the graphics generator (GG) A (coax 1) transmit data to the left DUs and the upper center DU; and the GG B (coax 2) transmit data to the right DUs and the lower center DU.
To operate the second test, select LSK 4L. This makes the graphics generator (GG) B (coax 2) transmit data to the left DUs and the upper center DU; and the GG A (coax 1) transmit data to the right DUs and the lower center DU.
Display Unit Display
When you operate the DU loop test, the display units show this information:
-DU location
-ARINC 429 loop status
-Remote light sensor brightness value
-Coax output source
-Coax cable input activity
-Bezel light sensor brightness value
-Unit brightness value.
737-700 MAINTENANCE TRAINING MANUAL
The DU location shows:
-LOB for left outboard
-LIB for left inboard
-CU for upper center
-CL for lower center
-RIB for right inboard
-ROB for right outboard.

An invalid DU location shows as BAD.
The ARINC 429 loop status shows the status of the ARINC 429 bus from the DU to the DEUs. A PASS or FAIL shows.
The remote light sensor brightness value shows as a percentage of maximum value. The range is 0 to 100. BAD shows if the input is bad.
The coax output shows the GG that transmits data to the display unit. The sources show as:
-1 for GG A in DEU 1 or DEU 2
-2 for GG B in DEU 1 or DEU 2.

The coax cable input activity shows the status of the four coax cable inputs to the DU. A Y for yes and a N for no shows. A white highlight box shows around the specific coax cable input that currently transmits to the DU. From left to right the letters refer to these coaxial couplers:
-First letter for coax coupler 1 from DEU 1, GG A
-Second letter for coax coupler 2 from DEU 1, GG B
-Third letter for coax coupler 4 from DEU 2, GG A
-Fourth letter for coax coupler 3 from DEU 2, GG B.

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737-700 MAINTENANCE TRAINING MANUAL
CDS BITE PAGES - DU LOOP TEST
The bezel light sensor brightness value shows as a percentage of maximum value. The range is 0 to 100. BAD shows if the input is bad.
The unit brightness value shows as a percentage of maximum value. The range is 0 to 100. BAD shows if the input is bad. This value changes if you change the unit brightness with the brightness controls.
The WXR brightness value shows as a percentage of maximum value. For the left inboard, and right inboard, the range is 0 to 100. BAD shows if the input is bad. This value changes if you change the unit brightness with the brightness controls. For the left outboard, right outboard, and upper center display units, the value 0 shows.
For the lower center display, the WXR value will change as you rotate the the brightness control, even though we do not display WXR information on the this DU.
　
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