So what does the Net City/New Net City link PCB work with?

[rewrite]

Noticed that in my NNC there are not one but TWO of those little link PCB's. Communication PCB's? I'm not sure what they're called. Are they like the CPS2 link kit which is only useful for a game or two, or will this work with a variety of software?

I'm referring to this board:
http://imgur.com/vI2DbG8

 

[Darksoft]

I read something about it here:
http://forum.arcadeotaku.com/viewtopic.php?f=3&t=20974

It has one input and two outputs so I guess it's a splitter so you can see on two cabinets/monitors what's been output buy ONE PCB.