What is the underlying algorithm of "Find threshold"

I understand that the "Find threshold" operator uses ROC to determine the best threshold. But, what kind of algorithm it uses to select the threshold? For example, (1) optimizes the precision and recall, or (2) something like this: http://stats.stackexchange.com/questions/29719/how-to-determine-best-cutoff-point-and-its-confidence-interval-using-roc-curve-i, or (3) other

Thanks!