EIA-232 Modem Cables DB-25 to DB-9

The wiring diagram for a DB-25 to DB-9 modem cable is shown in Table 1.

Table 1:  EIA-232 DB-25 to DB-9 modem cable

From DB-25	Signal	Direction	Signal	To DB-9
8	DCD		DCD	1
3	RxD		RxD	2
2	TxD		TxD	3
20	DTR		DTR	4
7	SG		SG	5
6	DSR		DSR	6
4	RTS		RTS	7
5	CTS		CTS	8
22	RI		RI	9
Shell	GND		GND	Shell

NOTES:

• Altpin should be turned off when using this cable.
• This cable utilizes the CTS signal of the modem for hardware flow control (RTS/CTS).
• EIA-232 cables cannot exceed 2500pF.  For information about calculating capacitance of your cable, click here.
• For information regarding the EIA-232/EIA-422/EIA485 specifications, click here.