Minecraft wiki entry for Pulse, associated text: While waiting for the input to turn on, the sticky piston is actually in a state where it is powered but doesn't know it (like a stuck-piston BUD circuit) until "woken up" by the input changing its power level. This will only work as long as the input power level is different than the resting output of the powered comparator (unintuitively, it will even work if the input power level is less than the comparator output).
Caveats:
- Any block or redstone update near the powered & stuck sticky piston can trigger it, so care should be taken to keep other circuit activity away from the sticky piston.
- The timer/counter part starts after the rising edge of the input pulse. -> At worst the output pulse is only "input_pulse + extender_time/2" not "input_pulse + extender_time". For "input_pulse < extender_time/2" it's always just "extender_time".