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

	DB25 pin D-SUB male at the DTE (Computer)
	DB25 pin D-SUB female at the DCE (Modem)

Pin	Name	Direction	Description
1	GND		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	-	-	RESERVED
10	-	-	RESERVED
11	STF	—»	Select Transmit Channel
12	S.CD	«—	Secondary Carrier Detect
13	S.CTS	«—	Secondary Clear to Send
14	S.TXD	—»	Secondary Transmit Data
15	TCK	«—	Transmission Signal Element Timing
16	S.RXD	«—	Secondary Receive Data
17	RCK	«—	Receiver Signal Element Timing
18	LL	—»	Local Loop Control
19	S.RTS	—»	Secondary Request to Send
20	DTR	—»	Data Terminal Ready
21	RL	—»	Remote Loop Control
22	RI	«—	Ring Indicator
23	DSR	—»	Data Signal Rate Selector
24	XCK	—»	Transmit Signal Element Timing
25	TI	«—	Test Indicator

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