This adapter is designed to allow your TI-99/4a to work with standard Atari 2600-style joysticks. The original design for the TI-99 had two joysticks connected via a ‘Y’ cable. While these joysticks were decent for their day, it is difficult to repair the original TI Joysticks today. We offer this board as a solution to that issue. You can use any Atari 2600, Commodore 64 and even the original Sega Genesis (with some conversion) controllers now. Simply plug in the board to the side of your TI, and plug your joysticks in to it and away you go!
Greg Thompson has been kind enough to design a new 3D printed case for this adapter! You can find his files along with photos of the case on Thingiverse here: