Minecraft wiki entry for Memory, associated text: This latch will maintain the highest signal level that arrived from input S if R is off, and fade (reduce memorized signal strength) by strength of R every two redstone ticks. For maximum strength (15) signals it behaves like any other RS latch, but it can also memorize intermediate signal levels, and since 2-tick pulses on R will subtract their strength from its memorized state, it makes a nice element of counter or countdown circuits.