(b)  
Push the button adjacent to OTHER FUNCTIONS.

 (c)  
Push the button adjacent to INPUT MONITORING.

 (d)  
Push the E/070/271/00 buttons on the CDU scratchpad.

 (e)  
Push the 1L line-select key.

 (f)  
Look at bit 21.

 NOTE: Bit 21 of this string is the AIR/GND bit for the
____ alternate sensing system. The far left bit is 32 and the far right bit is 17 in the top line of the binary data.
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747-400 MAINTENANCE MANUAL
 S 712-030
 (4)  
Do a check of the primary air/ground relay system for the air mode or the ground mode.

 (a)  
Push the next page button on the CDU to show the next Input Monitoring screen that is empty.

 (b)  
Push the E/070/273/00 buttons on the CDU scratchpad.

 (c)  
Push the 1L line-select key.

 (d)  
Look at bit 21.

 NOTE: Bit 21 of this string is the AIR/GND bit for the primary
____ sensing system. The far left bit is 32 and the far right bit is 17 in the top line of the binary data.
 S 862-031
 (5)  Remove electrical power (AMM 24-22-00/201), if it is not necessary.
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747-400 MAINTENANCE MANUAL
 PROXIMITY SWITCH ELECTRONICS UNIT (PSEU) - MAINTENANCE PRACTICES
________________________________________________________________
 1.  General_______
 A.  This procedure contains tasks to remove incorrect PSEU FAIL messages from the CMC present leg faults. To remove an incorrect PSEU FAIL message you must supply a new flight leg or erase the PSEU memory. The PSEU FAIL message will come into view again if the PSEU is defective.
 B.  This procedure contains these tasks:
 (1)  A task to supply a new flight leg to the airplane (Engine Operation Procedure)
 NOTE: It is necessary to operate the engine in this task.
____
 (2)
A task to erase the PSEU Memory (CMC Ground BITE Test Procedure).

 C.  
It is only necessary to do one of the applicable tasks to erase or clear the PSEU memory.

 TASK 32-09-03-862-001
 2.  Supply a New Flight Leg to the Airplane (Engine Operation Procedure)_______________________________________
 A.  General
 (1)  
To do this task you must operate an engine. This task will supply the airplane with a new flight leg. You can only supply one new flight leg.

 (2)  
Before you do this procedure, make sure that the electrical power sources supply satisfactory power. Power sources that are unsatisfactory can cause a PSEU FAIL message that will not go away.

 B.  
References

 (1)  
AMM 32-09-02/201, Air/Ground Relays

 (2)  
AMM 32-09-03/401, Proximity Switch Electronics Unit

 (3)  
AMM 32-09-03/501, Proximity Switch Electronics Unit

 (4)  
AMM 71-00-00/201, Power Plant (Operating Procedure)

 (5)  
AIPC 32-61-01, Fig. 2

 (6)  
WDM 32-61-11

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747-400
MAINTENANCE MANUAL

 C. Access
 (1)  
Location Zone
 221 Control Cabin, LH
 222 Control Cabin, RH

 D.
　
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