As you know, the Arduino micro controller only has a USB port and a TTL UART interface, so if you need an RS232 port directly connected to your Arduino, look no further than the RS232 Shield.

The RS232 serial port used to be the standard connection for most peripheral ports on PCs, but now the port is primarily used on industrial equipment and automation prototyping.
With the RS232 Shield and its DB9 connector, you can now easily access those elements straight from your Arduino.

This rev of the RS232 Shield provides you with the option to choose between two pins from an Arduino (D0 to D7) as software serial ports to communicate with RS232 Shield.
Also headers are included with this shield but will need to be soldered on by the end user.

Documents:

• Schematics
• Datasheet (MAX232)
• Product Wiki