RS-232 Connector Pinout Reference

The following are the pin connections for a DTE (data terminal equipment) device. This is the configuration used by a PC serial port. Devices such as modems and printers are normally configured as a DCE (data communications equipment).

DB-25 Pin	DB-9 Pin	Mnemonic	Direction	Description	Use
1		FG		Frame Ground	*
2	3	TD		Transmitted Data	A
3	2	RD		Received Data	A
4	7	RTS		Request to Send	B
5	8	CTS		Clear to Send	B
6	6	DSR		Data Set Ready	B
7	5	SG		Signal Ground	A
8	1	DCD		Data Carrier Detect	C
9				Positive DC Test Voltage	E
10				Negative DC Test Voltage	E
11		QM		Equalizer Mode
12		SDCD		Sec. Data Carrier Detect
13		SCTS		Sec. Clear to Send
14		STD		Sec. Transmitted Data
15		TC		Negative DC Test Voltage	D
16		SRD		Sec. Received Data
17		RC		Receiver Clock	D
18				Unassigned
19		SRTS		Sec. Request to Send
20	4	DTR		Data Terminal Ready	B
21		SQ		Signal Quality Detect
22	9	RI		Ring Indicator	C
23				Data Ready Selector	E
24		TC		Ext. Transmitter Clock	D
25				Unassigned