Minecraft wiki entry for Transmission, associated text: Because the redstone dust is not adjacent to any power or transmission components, only opaque blocks, it does not configure itself to point in any particular direction. This also causes the dust to power any opaque blocks or mechanism components to the side of the analog wire. Transmission components should not be placed adjacent to the wire's dust because that would cause the dust to configure itself in a way where it doesn't power the rest of the analog wire.