Minecraft wiki entry for Telegraph, associated text: An erasing device, though it can be as simple as an exposed, destroyable piece of the loop, is generally a lever wired to the custom NOR gate. Although they do take extra space, receiver loops should be built so that the input is on the opposite side of the NOR gate, so that no wires should have to cross paths. Also, remember, you can always use multiple levels of wire to avoid other parts of the telegraph.