I am trying to understand what code is doing.

PULSIN InputPin, ActiveState, FilteredSignal
'(receives the pulse from inputpin. What does Activestate do? You have it CON 1)

WHILE 1
PULSIN InputPin, ActiveState, InputSignal
FilteredSignal = FilteredSignal * (Samples - 1)
'(FilteredSignal =FilteredSignal multiplited by(20-1)

FilteredSignal = FilteredSignal + InputSignal
'(Then the same signal is added to the Inputsignal)

FilteredSignal = FilteredSignal / Samples
'(Then this signal is divided by 20)
PULSOUT OutputPin, FilteredSignal
'(results to outputpin)
WEND