I'm finding what appear to be two different descriptions of how FM encoding on early floppies worked.
In this description (see page 2 if it didn't go there directly) it appears that FM is nothing more than a clock pulse plus another pulse for a 1 and no pulse for a 0. So at the end of every window, the disk is in the "low state" and ready to encode the next window's clock as a rising edge.
However, Wikipedia's description appears different. It has a clock pulse wither rising or falling at the leading edge of the window, based on the result of the last bit. So in the case of a 1, you might get a rise-then-fall, or a fall-the-rise, depending on what preceded it.
I'm not sure the two are even illustrating the same thing, but I'm confused in any event. Can anyone clarify?