pin	signal	PC	...	Modem
3	TxD		→
2	RxD		←
7	RTS		→
8	CTS		←
4	DTR		→
6	DSR		←
1	DCD		←
9	RI		←
5	SG		←

http://www.aggsoft.com/rs232-pinout-cable/pinout-and-signal.htm

Charlie Root