File:BT GameCart back Mini-DIN-8.jpg

Back of a BT GameCart for the Super Nintendo Entertainment System, to be used in conjunction with an Apple Interactive Television Box (Voyager 2000 Interactive TV System in the UK) as part of British Telecom's interactive television market trials. The round connector is a Mini-DIN-8 RS-422 serial port, typically found on Macintosh systems.

Source

 * Any idea what this is? by Cameron James, Assembler Games. 2016-07-09.