[lemma=pulse] □ □
[lemma=pulse] [□] □
[lemma=pulse] (□ | □) □
Right from the equation we can see that depends not only from the symbol being sent ( from the change in the sign ) , but it can be seen that is also depends on which means that the pulse also depends on what was previously sent . The key to the researchers ' X-shaped light bullets is that the frequency of each component of a pulse also depends on its angle , and the angles formed by the X shape lead to a particular dispersion of the pulse 's components .