This is the pin layout of the HP serial cable 5062-3074:

(9 pin on one end, 78 pin at the other end)


Pin numbering on the 9pin plug (as you look into the plug):

 /            /
 -------------
 \ 1 2 3 4 5 /
  \ 6 7 8 9 /
    -------

Pin numbering on the 78pin plug (as you look into the plug):

 /                              /
 -------------------------------
 \ 1         11 12         20 /
  \ 21      30 31         39 /
   \ 40      50 51       59 /
    \ 60      70        78 /
     ---------------------


 And finally, the pins are connected as:

 9pin plug  |  78pin plug
 ------------------------
     1      |      31
     2      |      70
     3      |      --
     4      |      30
     5      |      --
     6      |      51
     7      |      12
     8      |      11
     9      |      50