New Description
The board on the side of the MK where you plug the pad I/O ("JAMMA" harness) and lights (three other connectors) into. Audio and VGA are also ran through this board on early revisions of this board (~MK3/MK4).
Variations of this board have been in use since the MK3. As the PIU LX cabinet uses different connectors for IO, this board is no longer needed for this cabinet.