On photocells multiple contacts add the option to select first or last contact
In exercises of change of direction, if the photocell is in the point where the subject change the sense of movement but not the direction the criterion of the longest contact is not good. If the subject makes two contacts because he/she passes the barrier (1st contact) and returns (2nd contact) sometimes the longest is the first and sometimes is the second. This makes that the times of each lap are very different and it's not possible to compare tests. One possible solution is to use always the first or last contact.