APC BackUPS dumb cable (on-battery only)

This cable can only be used on voltage-signalling UPSes, and apparently only provides the On Battery signal. As a consequence, this cable is pretty much useless, because all APC UPSes support more than just On Battery.

     
     Signal Computer                  UPS
            DB9F                     DB9M
      DCD    1   --------------------  2  On Battery
     
                   3.3K ohm
      TxD    3   --[####]-*
                          |
      DTR    4   ---------*
      GND    5   ---------------*----  4  Ground
                                |
                                *----  9  Common

not sure the following diagram is correct