"Com Port" is typically used to describe an RS-232 connector on a PC--which can be a DB-9 (originally it was a DB-25, for a good explanation on serial ports look here).
The CFA-634 is compatible with RS-232 and has a DB-9 connector that is compatible with a PC's DB-9 RS-232 Com Port.
Connection between a PC's DB-9 RS-232 Com Port and a CFA-634 requires a "straight" cable.