Thanks for the responses. The analog switch pictures are great. I am wondering how the optical switch functions. I will call the manufacturer and ask that question. Price is good. I was at the field yesterday when a large gas plane would not idle and consequently did not want to land. I have just built a gas plane and realized the possibility that I could get myself in the same situation and decided to add a kill switch to the ignition. I am also concerned about the danger of landing a plane and taxing off the runway while accidently hitting the throttle. If something causes the plane to idle to fast, I would like to be able to kill the engine on the approach and dead-stick-it to a landing. I will pursue buying the optic switch. Sorry, about not using the right forum but I still consider myself a beginner. I will do better next time....thanks again</p>