Failsafe plugs in to your receiver where your throttle and brake servo goes then you plug in the throttle servo in to it. Then you set the failsafe to do what ever you want if you lose the signal. I have mine set which now are built in to my radio where if it goes in the failsafe mode it puts the throttle back to idle and applies the brakes. Now the ones I have heard about with the temperature probe most have problems with them. If you look back a page you will see the green box mounted on the deck of my Rush that is the failsafe.