DB25 serial (RS232) port. Pinout and signals for the PC RS232 connector

DB25 pin D-SUB male

Pin	Name	Direction	Description
1	SHIELD	-	Shield Ground
2	TXD	—»	Transmit Data
3	RXD	«—	Receive Data
4	RTS	—»	Request to Send
5	CTS	«—	Clear to Send
6	DSR	«—	Data Set Ready
7	GND		System Ground
8	CD	«—	Carrier Detect
9	n/c	-
10	n/c	-
11	n/c	-
12	n/c	-
13	n/c	-
14	n/c	-
15	n/c	-
16	n/c	-
17	n/c	-
18	n/c	-
19	n/c	-
20	DTR	—»	Data Terminal Ready
21	n/c	-
22	RI	«—	Ring Indicator
23	n/c	-
24	n/c	-
25	n/c	-

Note: Direction is DTE (Computer) relative DCE (Modem).
Note: Do not connect SHIELD(1) to GND(7).