USB 1.1 to Serial Port DB9 RS232 Convertor. If you need a serial port but your computer doesn't have one, this USB to serial adapter is just the thing. Just plug the USB 1.1 compliant cable in to your system and there you go. It is also compatible with legacy operating systems. If you need to go serial, this adapter is for you. IOCrest USB 11 to Serial Port DB9 RS232 Convertor Adapter. Syba SY-ADA15006 USB A Male to Serial Cable DB9 (RS232) (3 feet).