The RS232 to TTL conversion shield is specially designed for UNO R3 control board, very convenient to change the serial port into RS232 interface.
The shield comes with a DB9 connector（male head）, easy to connect various RS232 interface equipment. It also comes with a RS232 pin header for connection and debugging.
It even comes with soldering area for DIY design, so you can make full use of this shield. On the shield there is a programming mode control switch; turn OFF for burning the program to UNO R3; turn ON for normal use.