Minecraft wiki entry for Redstone_mechanics, associated text: Circuits with a stable output are said to produce a signal — an ON signal (also "high" or "1") if powered, or an OFF signal ("low", "0") if unpowered. When a signal changes from OFF to ON ("rising edge") and then back to OFF ("falling edge"), that is described as a pulse (or ON pulse), while the opposite is described as an OFF pulse. ON pulses are far more common, and in casual discussion, "a signal" often refers to an ON pulse.