xterminator

I want to trigger a 555 with a positive AND negative gooing flank. How can I accieve this ? The 555 is controlled via a switch, the switch remains closed or open, longer than the one shot of the 555. I already have built a coupling cirquit with some resistors and a capacitor. It now triggers at a negative flank, but this same thing should also happen with an positive gooing flank. Here is the schematic I already have so far: http://users.telenet.be/xterminator/controller.pdf I've drawn a little graph of my needs. The spike may be reversed (negative gooing). Then I don't need to reverse it anymore, to trigger the 555