Posted on 2004-04-02
I know this likely isn't the place to ask this, but I couldn't find anywhere else...
Does anyone know of an electronic component that works kind of like a transistor, only it turns on when the electricity stops?
I have a pocket radio in my truck because the FM radio is broken, and I'm trying to build something that will switch between power from a cigarett lighter adapter and two AAA batteries. I need it to switch to the cigarett lighter adapter when the power starts comming from that, and for it to switch to the batteries when the truck is turned off and the cigarett lighter adapter stops providing power.