D-sub 9 Connector Pinout
Pinout and diagram of DE9 connector (DB9 connector), commonly used for serial ports (RS-232).
Pin | SIG. | Signal Name | DTE (PC) |
---|---|---|---|
1 | DCD | Data Carrier Detect | in |
2 | RXD | Receive Data | in |
3 | TXD | Transmit Data | out |
4 | DTR | Data Terminal Ready | out |
5 | GND | Signal Ground | - |
6 | DSR | Data Set Ready | in |
7 | RTS | Request to Send | out |
8 | CTS | Clear to Send | in |
9 | RI | Ring Indicator | in |
The DTE (PC) has the male connector (shown below), and the DCE (peripheral) has the female.

RS-232 Maximum Cable Length
The maximum cable length for RS-232 is 50ft, but in practise depends on baud rate, cable specific capacitance and ambient noise. The table below contains some rules-of-thumb from experiments done by Texas Instruments years ago.
Baud rate | Maximum range / cable length |
---|---|
19200 | 50ft |
9600 | 500ft |
4800 | 1000ft |
2400 | 3000ft |
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