RS232 DB9 Connector

DB-9M	Function			Abbreviation

Pin #1	Data Carrier Detect		CD
Pin #2	Receive Data			RD or RX or RXD
Pin #3	Transmitted Data		TD or TX or TXD
Pin #4	Data Terminal Ready		DTR
Pin #5	Signal Ground			GND
Pin #6	Data Set Ready			DSR
Pin #7	Request To Send			RTS
Pin #8	Clear To Send			CTS
Pin #9	Ring Indicator			RI


RS-232 Serial PC Port Connector DB-25

DB-25M	Function			Abbreviation

Pin #1	Chassis/Frame Ground		GND
Pin #2	Transmitted Data		TD
Pin #3	Receive Data			RD
Pin #4	Request To Send			RTS
Pin #5	Clear To Send			CTS
Pin #6	Data Set Ready			DSR
Pin #7	Signal Ground			GND
Pin #8	Data Carrier Detect		DCD or CD
Pin #9	Transmit + (Current Loop)	TD+
Pin #11	Transmit - (Current Loop)	TD-
Pin #18	Receive + (Current Loop)	RD+
Pin #20	Data Terminal Ready		DTR
Pin #22	Ring Indicator			RI
Pin #25	Receive - (Current Loop)	RD-