Thanks. Should work for Ataris. I think we're probably SOL on ColecoVision and maybe Segas, which I believe have two grounds depending on state (e.g., for CV state 1 is joystick, left button and pin 8 as ground, state 2 is keypad and right button with pin 5 as ground). Although, you could use one on the CV steering wheel which only uses state 1.
This one works well. No problems. Data Shield DB9 surge protector. These are a little pricey. Watch for a deal for $10 or so.
This one causes both fire buttons to work at once with fire 1 (L button), for some reason. B&B DB9 surge protector. You also have to do a lot of hacking away to remove bits that interfere with plugging the cable in. With the Data shield, you just have to unscrew the dealies on the sides. BTW, this ad has them for $45 a piece (not for 4). I paid $11 for mine.