Ok, the voltage spike... not sure what that is, but it's nice to know what was causing my confusion.
Also, is this double frequency? If you look at my "B" or the second half of your drawing, (which are similar) ... that shows one "pulse" for each "high and low"
and another thing i just noticed, in your first scope shot, the pulse starts on "high" and ends on a "low", whereas on your second scope shot the pulse starts on "low" and ends on a "high" .. i didn't notice this when i drew my first picture, and i drew them both as "low"-"high", but the difference is probably significant.
in your picture you drew them both as "high"-"low"
feel free to ignore me and deal with more important experiments and explanations, i am just curious, and i'll figure this out when i get my hands dirty.