From Wikipedia: "An electronic speed control or ESC is a device mounted onboard an electrically powered radio control model in order to vary its drive motor's speed, its direction and even to act as a dynamic brake in certain controllers." I think I kind of understand it but need to read up a bit more on it. [[link=http://en.wikipedia.org/wiki/Electronic_speed_controller]http://en.wikipedia.org/wiki/Electronic_speed_controller[/link]]

Tx is transmitter and that's the controller thing that you're holding. Related to this is Rx, which is receiver, I believe, and that's the thing that's receiving the signal from the Tx that's on your chopper's electronic board.

I'm pretty sure (someone correct me if I'm wrong) the CP and the CX2 will have all the above.