RS423 Serial Port Connector Pin Layout

RS-423 is a serial communications standard that provides asynchronous communication capabilities, such as hardware flow control, software flow control, and parity check. It has been widely used for decades. Unlike RS-232, RS-423 is capable of data transmissions over long distances (up to 4000 Feet).

The following document describes the functions of the pins on the RS423 25 and 37 pin Sub-D connectors used in serial communications. The pins in the images are as viewed from the pin side (not the solder or printed circuit board side). The male sockets are used on the DTE (Data Terminal Equipment ) or PC side. The female sockets are on the DCE (Data Communication Equipment ) or Modem Side.

Using the ActiveXperts Serial Port Component you can send and receive data and control the RS423 port.

RS423 25 Pin connector (DB-25)

1	GND	Shield
2	TDA	Transmitted Data A
3	RDA	Received Data A
4	RTSA	Request To Send A
5	CTSA	Clear To Send A
6	DSRA	Data Set Ready A
7	GND	Signal Ground
8	RLSDA	Receive Line Signal Detect A
9	RTA	Receive Timing A
10	RLSDB	Receive Line Signal Detect B
11	XTB	External Timing B
12	TTB	Transmit Timing B
13	CTSB	Clear To Send B
14	TDB	Transmit Data B
15	TTA	Transmit Timing A
16	RDB	Received Data B
17	RTA	Receive Timing A
18	LL	Local Loopback
19	RTSB	Request To Send B
20	DTRA	Data Terminal Ready B
21	RL	Remote Loopback
22	DSRB	Data Set Ready B
23	DTRB	Data Terminal Ready B
24	XTA	External Timing A
25	TM	Test Mode Indicator

RS423 37 Pin connector (DB-37)

1	GND	Ground
2	SRI	Signal Rate Indicator
3	-	Reserved
4	TDA	Transmit Data A
5	TTA	Transmit Timing A
6	RDA	Received Data A
7	RTSA	Request To Send A
8	RTA	Receive Timing A
9	CTSA	Clear To Send A
10	LL	Local Loopback
11	DSRA	Data Set Ready A
12	DTRA	Data Terminal Ready A
13	RLSDA	Receive Line Signal Detect A
14	RL	Remote Loopback
15	IC	Incoming Call
16	SF	Select Frequency
17	XTA	External Timing A
18	TMI	Test Mode Indicator
19	GND	Ground
20	RC	Receive Common
21	-	Not Connected
22	TDB	Transmit Data B
23	TTB	Transmit Timing B
24	RDB	Receive Data B
25	RTSB	Request To Send B
26	RTB	Receive Timing B
27	CTSB	Clear To Send B
28	TIS	Terminal In Service
29	DSRB	Data Set Ready B
30	DTRB	Data Terminal Ready B
31	RLSDB	Receive Line Signal Detect B
32	SS	Select Standby
33	SQ	Signal Quality
34	NS	New Signal
35	XTB	External Timing B
36	SB	Standby Indicator
37	SC	Send Common