Without going init details, if you know how to design a "window" circuit, implement a NOT function with an opamp at the output of that "window" circuit and you will have "antiwindow" circuit, whatever it is ..
Regards,
IanP
well
a window circuit is normally built wih the help of opamps working as comparators, if our input voltage lies with in a range(window) then our output will be +ve ref. volatge , otherwise -ve ref