Distribution of all detected period pulsed fractions (defined as the semi-amplitude of the sinusoid divided by the source average count rate) vs. source counts. The blue dots correspond to observations that are affected by counting-mode switches. The red dots correspond to periods detected in observations that are not (or almost not) affected by the counting-mode switch. Histograms of the PFs and counts are presented at the top and left, respectively, for the two datasets.