DB25 pinout and signals for the PC RS232 connector. COM Port

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).

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