its a mix out of a big old analog switch and some LSD
sometimes you will see colors and other cool effects
...
the switch is electronic, it needs a signal (low/high) to select one of the both sources
the second part is "switchcontrol", this tool detects every change of the monitorid/screenmode
switchcontrol is providing the electronic with the correct low or high signal, depending on the used screenmode
signal will be given by the 8520-ic
