RS232 DB9 Pinout

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RS232 DB9M.gif

Pin Name Notes/Description Direction
1 DCD Data Carrier Detect In
2 RD Receive Data (a.k.a RxD, Rx) In
3 TD Transmit Data (a.k.a TxD, Tx) Out
4 DTR Data Terminal Ready Out
5 SGND Ground N/A
6 DSR Data Set Ready In
7 RTS Request To Send Out
8 CTS Clear To Send In
9 RI Ring Indicator In


Null Modem Adapter

Male Signal Male Signal
2 RD 3 TD
3 TD 2 RD
4 DTR 6,1 DSR, DCD
6,1 DSR, DCD 4 DTR
7 RTS 8 CTS
8 CTS 7 RTS
5 SGND 5 SGND
9 RI 9 RI