Computer Com Port (RS-232/V.24 pin out on a DB-9)

RS232/V.24 DB9 pinout and signals
Fig.1 RS232/V.24 DB9

Pin Name 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

X.21 interface on a DB 15 connector

X.21 interface on a DB 15 connector
Fig. 2. X.12 DB15 connector

RJ-45 RS232 connector

EIA-561 defined RS232 on RJ 45 (modular) connector. It can be used only for nonsynchronous applications onlym because it does not have synchronous clocking signals. Note: The RI pin (#1) sometimes can be used as DSR.

RJ45 RS232 connector
Fig.3. RJ-45 RS232 connector

RJ45 RS232D connectors (same as telephone connectors)

RS232D uses RJ45 type connectors (similar to telephone connectors)

Pin No. Signal Description Abbr. DTE DCE
1 DCE Ready, Ring Indicator DSR/RI
2 Received Line Signal Detector DCD
3 DTE Ready DTR
4 Signal Ground SG    
5 Received Data RxD
6 Transmitted Data TxD
7 Clear To Send CTS
8 Request To Send RTS

DB25 V.24 pinout and signals

DB25 X24 pinout ans signals
Fig.4. RS232 V.24 connector

DB25 V.24 pinout and signals (ALT A connector)

DB25/V24 pinout ans signals
Fig.5. RS232 V.24 (ALT A) connector

RS232 DB25 all pins (some applications require more pins)

RS232 DB25 full pinout (all pins)
Fig.6. RS232 DB25 connector

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