Cable Labels for Optical Splitters
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TSF module slot assignment as seen from the BACK of the rack 23.
crate slot = physical slot numbers as printed on crate by manufacturer 
slave slot = logical slot number the DCC uses to address the board 

TSFY crate (top of rack)
TSF name    Y4      Y3      Y5      Y2      Y6      Y1      Y7      Y0     
crate slot  21      19      17      15      13      11       9       7     
slave slot  15      13      11       9       7       5       3       1    

TSFX crate (bottom of rack) 
TSF name    X8  X7  X9  X6 X10  X5 X11  X4 X12  X3 X13  X2 X14  X1 X15  X0 
crate slot  21  20  19  18  17  16  15  14  13  12  11  10   9   8   7   6 
slave slot  15  14  13  12  11  10   9   8   7   6   5   4   3   2   1   0

a) We need a switch panel of feedthroughs between crate 1 & 2 (top&middle)
   which has 8+1  (1=spare) channels
                                          normal   spare
   Labels:  splitter input                Y*       Spare-Y
            after split long leg end      Y*L      Spare-YL
            after split short leg end     Y*S      Spare-YS
   where *=0-7 depending on which slot they serve. 
b) We need a switch panel of feedthroughs below crate 3 at the bottom 
   which has 16+2 (2=spares) channels     
                                          normal   spare
   Labels:  splitter input                X*       Spare-X#
            after split long leg end      X*L      Spare-X#L
            after split short leg end     X*S      Spare-X#S
   where *=0-15 depending on which slot they serve.
     and #=A,B.