This is a custom personal computer which I assembled to be an all-in-one machine. Not only does it contain generic PC hardware, but it also contains a flatscreen VGA/TV display device, and also NES machine hardware. I use FDS loader inside this thing for real NES application development.
The 4-way switch is a diagram documenting the implementation of an electronic circuit inside the PC devkit, which would multiplex the controller signals coming from the parallel port (of a PC emulator), with those from the internal NES hardware (also within the unit). There would be 4 front jacks for controller hook-ups, 2 for SNES and 2 for NES. I have yet to build this hardware.