are few advantages for analyzing only active periods. The main one is that a lower $ N_{var} $ can be used during these periods with smaller risk of finding false peaks. The risk of finding false peaks due to a Poisson noise depends on the time scale in which the original signal (i.e. without the noise) changes its count rate in the same order as the Poisson noise level. If the signal is constant (no real pulses), then this time scale is as long as the signal. If the constant signal is longer, it contains more time bins with the same level of Poisson noise counts. Hence, there is a larger chance of finding within these time-bins three time-bins, $ t_{p} $, $ t_{1} $ and $ t_{2} $, that satisfy the criterion in Li & Fenimore algorithm. Then $ t_{p} $ would become a false peak. On the other hand, if the signal is changing monotonically then the length of the signal is irrelevant. $ t_{p} $, $ t_{1} $ and $ t_{2} $ must be within the period in which the signal changes at the same order as the Poisson noise level; there is no chance of finding 