RS232 port (DB-25 pin). Pinout and signals for full RS232 connector

DB25 pin D-SUB male at the DTE (Computer)
DB25 pin D-SUB male at the DTE (Computer)
DB25 pin D-SUB female at the DCE (Modem)
DB25 pin D-SUB female at the DCE (Modem)

Pin Name Direction Description
1
GND
Shield Ground
2
TXD
—»
Transmit Data
3
RXD
«—
Receive Data
4
RTS
—»
Request to Send
5
CTS
«—
Clear to Send
6
DSR
«—
Data Set Ready
7
GND
System Ground
8
CD
«—
Carrier Detect
9
-
-
RESERVED
10
-
-
RESERVED
11
STF
—»
Select Transmit Channel
12
S.CD
«—
Secondary Carrier Detect
13
S.CTS
«—
Secondary Clear to Send
14
S.TXD
—»
Secondary Transmit Data
15
TCK
«—
Transmission Signal Element Timing
16
S.RXD
«—
Secondary Receive Data
17
RCK
«—
Receiver Signal Element Timing
18
LL
—»
Local Loop Control
19
S.RTS
—»
Secondary Request to Send
20
DTR
—»
Data Terminal Ready
21
RL
—»
Remote Loop Control
22
RI
«—
Ring Indicator
23
DSR
—»
Data Signal Rate Selector
24
XCK
—»
Transmit Signal Element Timing
25
TI
«—
Test Indicator
Note: Direction is DTE (Computer) relative DCE (Modem).
Note: Do not connect SHIELD(1) to GND(7).

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RS232 port related links

- RS232 to RS232 connect two DTE devices or computers using DB9 pin connectors.
- RS-232 - RS-232 connect two DTE devices or computers using DB25 pin connectors.
- Serial port interface serial port interface description.