TrackStarter plays the sounds: On your marks, set and go, as well as calculating your reaction time so you can practice sprint starts on your own, with other athletes, from blocks or from a standing position. TrackStarter allows the user to modify the time interval between the sounds so that the user can adapt it to their needs. Users can record new sounds and use them instead of the default sounds. USER GUIDE: STARTS - Place the phone in contact with the blocks (behind the back block for ex