RS-232

Male DB9 serial connector viewed from front. Reverse for female connector or back view of male connector.

9-Pin DB9 Assignments

1	DCD	Data carrier (line signal) detect
2	RXD	Receive data
3	TXD	Transmitted data
4	DTR	Data terminal ready
5	GND	(Signal) ground
6	DSR	Data set ready
7	RTS	Ready/request to send
8	CTS	Clear to send
9	RI	Ring indicator

Male DB9 serial connector viewed from front. Reverse for female connector or back view of male connector.

25-Pin DB25 Assignments

1		Shield - chassis/frame protective ground
2	TXD	Transmitted data
3	RXD	Receive data
4	RTS	Ready/request to send
5	CTS	Clear to send
6	DSR	Data set ready
7	GND	(Signal) ground
8	DCD	Data carrier (line signal) detect
9		Reserved for testing - positive voltage
10		Reserved for testing - negative voltage
11		Unassigned
12	SCF	Secondary received carrier (line signal) detect
13	SCB	Secondary clear to send
14	SBA	Secondary transmitted data
15	DB	Transmission signal element timing (clock)
16	SBB	Secondary received data
17	DD	Receiver signal element timing (clock)
18		Unassigned
19	SCA	Secondary request to send
20	DTR	Data terminal ready
21	CG	Signal quality detector
22	RI	Ring indicator
23	CH/CI	Data signal rate selector
24	DA	External transmit signal element timing (clock)
25		Test mode

RS-232