I want to add a PIR to an alarm system I have.. Only problem is all modern PIR's are supplied with 'normally closed' connections and I need one that is normally open. Yes, I could use a relay but that would mean it would be held open all the time and draw current.. This is in a battery powered situation and the extra current draw would not be welcome ! So I got to thinking.. What about a thyristor ? Only problem is, my bloody brain will not function and I am damned if I can figure out a way to use one .. Basically I can hard wire either the +ve or -ve feed and have whichever is left going through the switched line. I want it to have a feed to the -ve rail when there is no voltage applied to it.. So come on you clever buggers out there.. help !!!!