What Are Observers?

Observers detect any block change. The "face" detects while the red dot in the back sends a redstone signal so fast, pistons won't retract the block in front of them. The next pulse though, will retract it. To activate an observer, place or mine a block touching its "face". This works with redstone being powered, sugar cane or cacti growing, a cauldron getting filled, redstone ore getting stepped on or punched, or any other block changed.