The Control Module receives the launch signal that sends the Shockwave car down the track. It also receives the signal to stop the car. Though the two included in the Shockwave Starter Package are all you need to race, extras are handy for prepping the next round of cars.
The Control Module must be used with the Shockwave Electric Car Kit and the Starting Blocks from the Starter Package as well as a G3 or F1 race system with launch pods.