The trajectory is given by my coach who moves and tells me the trajectory to follow: "right" "left" "line".
The caller is a fixed marker which is placed to the right of the jump and indicates to me where the jump is located: "there" at each stride. He once tells me the word "axis" when he thinks that I am well oriented to cross the jump that I am far or near. The caller starts telling me the direction on each reception of the previous jump.
Tiffany made sure to use few words to tell me the direction and we made sure to use words that did not look alike.
There is also the feel of the horse that tends to go for its bar (when I feel he is a little further forward) :)