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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