It's an old term that may be called End Point Adjustment in your newer radio. It's where you adjust the amount of throw for the servos. Some people will just call it servo travel too. I'm having a brain fart and can't remember what the words would be for the ATV. Sorry, I'm sure someone else will remember what it stands for. Today it is termed EPA in most radios. I think JR was the last one to use the term ATV?