Minecraft wiki entry for Redstone_computers, associated text: Most often, making it volatile has no use in Minecraft, so the easiest way to make some is to use d-flip-flops and to add a reading and writing function. The bottom image shows instead of locking repeaters, it uses d-flip-flops which is much more space inefficient but simpler to build. D-flip-flops work more or less like locked repeaters, one input - if on, unlocks in until the input is off and the other will set it once unlocked. The output can be read as a bit and with a NAND gate, be ignored or put onto the bus. This is gone over in detail in the second chapter, Tutorial on building a Computer. Excuse the texture pack.