With the SKIP switch in open position the counter will count and
display the time between successive leading edges, while in the closed
position it'll display the time between every other leading edge by
ignoring the one in the middle, like this:

|----T1----|----T2----|----T3----|----T4----|---
_ _ _ _ _
IN1__| |__________| |__________| |__________| |__________| |__


|-----------T1----------|-----------T2----------|---
_ _ _ _ _
IN2__| |__________| |__________| |__________| |__________| |__



JF