DE-9
From Sega Retro
DE-9 is a D-shaped connector/port with two rows totaling 9 pins in an E-size connector. The top row has 5 pins, and the bottom row has 4 pins. Due to the fact that it is a serial port, transmission is done one bit at a time. DE-9 ports are commonly seen on PCs as RS-232C serial ports. They are also used on the Sega Genesis and Master System for connecting input devices, such as joypads. (Earlier revisions of the Sega Genesis had a third DE-9 port on the back of the console for a modem adapter.)
Two types of DE-9 connectors exist. A male DB-9 connector has pins, while a female DE-9 connector has holes. You can only plug a male connector into a female plug or vice versa, unless you have a DE-9 gender changer.
Images
Male DB-9
Female DB-9
