full:
DB25 DB9                    DB9 DB25
8    1    DCD----------RTS--\ 7    4
3    2    RxD----------TxD  | 3    2
2    3    TxD----------RxD  | 2    3
20   4    DTR----------DSR  | 6    6
7    5    SGND--------SGND  | 5    7
6    6    DSR----------DTR  | 4   20
4    7 /--RTS----------DCD  | 1    8
5    8 \--CTS          CTS--/ 8    5
     9    RI    N.C.    RI    9

RX/TX only:
	DB25 - DB25
		(2, 3, 7) --- (3, 2, 7)
	DB9 - DB9
		(2, 3, 5) --- (3, 2, 5)