My Spektrum DX3.0 came with two recievers and two servo's and you can program the transmitter for multiple cars. I have different transmitter profiles for the same car for different types of tracks. You can change the amount of steering, throttle, brakes etc. A really cool thing you can do is called Exponential sensitivity so you can adjust how sensitive your throttle, brakes or steering. Say you want to reduce your throttle sensitivity so you don't do burn outs every time you pull the trigger or you don't want your steering to be really touchy. You can change it the opposite way too so you can have a very unsensitive (i know that's not a word but it's early
) steering/throttle/breaks until you get to a certain percentage of your throttle/steering/breaks than it becomes really sensitive.