RS232

Common names: EIA-232D (RS232-D), ITU-TSS (CCITT) V.24/V.28, ISO 2110

[edit] Pinout

25 PIN D-SUB MALE at the DTE (Computer).

25 PIN D-SUB FEMALE at the DCE (Modem).

Pin	Name	RS232	V.24	Dir	Description
1	GND	n/a	101		Shield Ground
2	TXD	BA	103		Transmit Data
3	RXD	BB	104		Receive Data
4	RTS	CA	105		Request to Send
5	CTS	CB	106		Clear to Send
6	DSR	CC	107		Data Set Ready
7	GND	AB	102		System Ground
8	CD	CF	109		Carrier Detect
9	-			-	RESERVED
10	-			-	RESERVED
11	STF		126		Select Transmit Channel
12	S.CD	SCF	122		Secondary Carrier Detect
13	S.CTS	SCB	121		Secondary Clear to Send
14	S.TXD	SBA	118		Secondary Transmit Data
15	TCK	DB	114		Transmission Signal Element Timing
16	S.RXD	SBB	119		Secondary Receive Data
17	RCK	DD	115		Receiver Signal Element Timing
18	LL	LL	141		Local Loop Control
19	S.RTS	SCA	120		Secondary Request to Send
20	DTR	CD	108.2		Data Terminal Ready
21	RL	RL	140		Remote Loop Control
22	RI	CE	125		Ring Indicator
23	DSR	CH	111		Data Signal Rate Selector
24	XCK	DA	113		Transmit Signal Element Timing
25	TI	TM	142		Test Indicator

Notes:

Direction is DTE (Computer) relative DCE (Modem).
RS232 column is RS232 circuit name.
ITU-T column is ITU-TSS V.24 circuit name.

Value	Name	Voltage
0	Space	+3 to +12 VDC
1	Mark	-3 to -12 VDC

Note: -3 to +3 is undefined value.