DB9 pinout and signals for the PC RS232 connector (serial and RS232 ports)

DB9 pin D-SUB male
 DB9 pin D-SUB male

Pin Name Direction Description
1
 CD
«—
 Carrier Detect
2
 RXD
«—
 Receive Data
3
 TXD
—»
 Transmit Data
4
 DTR
—»
 Data Terminal Ready
5
 GND
System Ground
6
 DSR
«—
 Data Set Ready
7
 RTS
—»
 Request to Send
8
 CTS
«—
 Clear to Send
9
 RI
«—
 Ring Indicator
Note: Direction is DTE (Computer) relative DCE (Modem).

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RS232 pinout and signals
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