The ProtocolAnalyzer constantly samples the analog input signal, trying to recreate any digital pulses found in the signal. The so called //flank detector// uses a quite simple algorithm to find the flanks of the pulses:

//Find sequences where the sampled value changed significanlty (Flank Swing) over a short period of time (Flank Length)//

To avoid the same flank being counted twice if it is large, we wait a while (Flank Holdoff) after finding a flank until we  accept a new flank. This picture shows the meaning of the settings on a real sampled signal. The red line is the analog value (where the sample points are marked with black dots). The blue line is the flank detectors interpretation of the signal:

{{:analyzer:flank1.png|}}

In the example //Flank Swing// was set at 50 and //Flank Length// set to 3, so when the signal changed more than 50 over 3 samples, the flank was detected (see the blue line). Note that the signal changed more than 50 in the following samples as well, but since this was within //Flank Holdoff//, this was not counted.