Additional info conserning your case:
"Cabling of Duplicated Control on Wired Magazines
This Service Advice covers the cabling of Duplicated control systems on older type wired backplane magazines for software releases BC 8 and above.
Unlike the current PCB magazines (LPB16 etc), an additional cable is required to make duplicated control work on wired backplane magazines of the type LPB3, LPB9, LPB12 and LPB13. The cable required is TSR 901 0315/600. One cable is required for each magazine and is positioned between DSU:0 and DSU:1.
An example of the cabling for LPB9 magazines has been provided and would be the same for other type magazines. Please note the orientation of the additional cable as it has an ‘A’ and ‘B’ end.
Other points to note are that the LPU cannot reside in slot 73 and also the LPU should be in the same position in the bottom magazine as it is in the top. LSU’s should be located in the BSU slots and DSU’s in the SSU slots
The quarter plugs used for TSR 901 0315/600 cable are the piggy back type and all pins on the plug (odds and evens) should appear at the back of the plug. Only two wires are to be connected between the ‘A’ and ‘B’ ends. The piggy back plug is located between the DSU and the TSR 901 0440/xx cable."
Can't insert pic from that document.
Best regards
