(Ref. Fig. 002, 003)
 3. EIS Switching Operation
_______________________
 A. EIS DMC Switching
 There are no cross-talk links between the three DMCs, in order to ensure
 complete segregation of CAPT and F/O displays.

 Inside the DMCs, downstream of the PFD, ND, ECAM channels, there are
 switching relays for the DSDLs.

 In the event of DMC 1 (or DMC 2) failure, the Captain (or First Officer)
 can switch over to DMC 3. This is controlled by means of the EIS DMC
 selector switch (CAPT/3 or F/O/3 position).
 (Ref. Fig. 004)

R  In this case, the DMC 3 totally replaces the DMC 1 (or 2) through the
R  stage of the output switching relay of the failed DMC. As explained in the previous section, the connections between the DMC 3 PFD and ND channels and the PFDs and NDs are cross-wired.
 Therefore, it is necessary to send the DMC 3 PFD and ND signals to the Alternate inputs of the PFDs and NDs, so that the PFD and ND images remain at their normal location.
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 The selection of the alternate inputs of the PFDs and NDs is made by the
 relay box (CAPT or F/O)
 (Ref. Fig. 005)

 NOTE : In the event of DMC failure, the DUs driven by this DMC display a

____ diagonal line, which helps the crew in making immediately the right action.
 The DMC 3 acts as a back up (hot spare). When the EIS DMC selector switch is in NORM position, the DMC 3 works like the DMC 1 as regards the selection of all the input sources, so as to be readily available for taking over the driving of the CAPT PFD and ND and of the upper ECAM DU, with minimum transfer delay, as soon as the pilots place the ECAM/ND XFR selector switch in CAPT/3 position. In case of selection of the DMC 3, both the master DSDL and the feedback DSDL buses are switched in the DMC 1 (or 2) output switching stage.
 B. Switching of the EIS DUs (PFD-ND)
 (1)
 Manual PFD/ND transfer (Ref. Fig. 006) A manual transfer facility (by means of PFD/ND XFR P/BSW) enables each pilot to cross-change the images which are displayed on his PFD and ND at any time : at each action on this pushbutton switch, there is an inversion between the two images : the one which was displayed on the left DU is displayed on the right DU and vice versa.

 (2)
 Transfer of the PFD image on the ND

 (a)
 In case of detected failure of the DU normally displaying the PFD image, there is an automatic PFD/ND transfer. The PFD image is presented on the DU normally showing an ND image. This automatic transfer is controlled by means of a discrete signal generated by the DMC upon recognition of the failure (NORMAL PFD INVALID).

 (b)
 This transfer can also be obtained manually by the pilot, by either of the two following means :

 -either deactivate the PFD by setting ON-OFF/brightness potentiometer to OFF : this automatically transfers the PFD image on the ND and the ND image is replaced by the PFD image, - or press the PFD/ND XFR pushbutton switch.
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 EIS - DMCs/DUs Links & Reconfiguration Controls
 Figure 002

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 Master and Feedback DSDLs
 Figure 003

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 EIS (and ADIRS) - Transfer Selector Switches
 Figure 004

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 EIS - Alternate Inputs Selection
 Figure 005

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 EIS - PFD & ND Brightness & ON/OFF Controls
 PFD/ND XFR P/BSW
 Figure 006

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 (3)
 Transfer of the ND image on the PFD If the ND is deactivated (corresponding ON-OFF/brightness potentiometer set to OFF), or if the ND fails, there is no automatic transfer of the ND image on the PFD. However, the pilot can recover the display of the ND image on the remaining DU, normally showing the PFD image, by means of the PFD/ND XFR pushbutton switch.

 (4)
 Operation (Ref. Fig. 007) The PFD and ND transfers are controlled by the choice of the NORMAL and ALTERNATE inputs of the PFD and ND. For a given side (CAPT or F/O), an A/C circuitry sends a discrete signal in parallel to the PFD and ND on their AA-25 contact :
　
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