RS232 25 pin pinout. RS-232 was created for one purpose, to interface between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE) employing serial binary data interchange. So as stated the DTE is the terminal or computer and the DCE is the modem or other communications device. Free service manuals.

Connector pinout: RS232 25 pin

RS-232 was created for one purpose, to interface between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE) employing serial binary data interchange. So as stated the DTE is the terminal or computer and the DCE is the modem or other communications device.

At the DTE

At the DCE

pin	name	direction	description	color
1	GND	------	AA: Protective Ground
2	TXD	OUT	BA: Transmit Data
3	RXD	IN	BB: Receive Data
4	RTS	OUT	CA: Request to Send
5	CTS	IN	CB: Clear to Send
6	DSR	IN	CC: Data Set Ready
7	GND	------	AB: Signal Ground
8	CD	IN	CF: Carrier Detect
9	-	-	RESERVED - Positive test
10	-	-	RESERVED - Negative test
11	STF	OUT	Select Transmit Channel
12	S.CD	IN	SCF: Secondary Carrier Detect
13	S.CTS	IN	SCB: Secondary Clear to Send
14	S.TXD	OUT	SBA: Secondary Transmit Data
15	TCK	IN	DB: Transmission Signal Element Timing
16	S.RXD	IN	SBB: Secondary Receive Data
17	RCK	IN	DD: Receiver Signal Element Timing
18	LL	OUT	Local Loop Control
19	S.RTS	OUT	SCA: Secondary Request to Send
20	DTR	OUT	CD: Data Terminal Ready
21	RL	OUT	Remote Loop Control
22	RI	IN	CE: Ring Indicator
23	DSR	OUT	CH/CI: Data Signal Rate Selector
24	XCK	OUT	DA: Transmit Signal Element Timing
25	TI	IN	Test Indicator