I'm going to assume you mean an Engine Kill switch. There are two way to handle it. If your transmitter is a computer type, it most likely has a setting to set up the throttle to kill the engine. If you have one of the radios with manual trim, you just setup you throttle servo so that maximum trim to the off side fully closes the throttle when the stick is fully down. Most guys flying like this set up the throttle trim to mid point and then adjust the linkage for a good idle at full down on the stick. Then for the final kill, simply slide the trim down.

The computer setup works similuar, but the kill portion is linked to a switch that will cut the throttle even more, usually around 30% or so. The computer radios throttle trim only changes the low end, but the manual radios skews the full range of movement. I discovered this when I was on the buddy box and I was using an old radio hooked to my computer radio. Depending on the trim on the old, I could get either full throttle, or a slow idle but not both. I had one crash because of this I taxied back to the line and ask the instructor to kill the engine. He let loose of the trainer switch, but his throttle was full on and the plane lunged into the barrier and broke a wing.

Don