Observer

The Observer is a Redstone-related Block that was added in Update 0.15.0.

Crafting

 * 6 Cobblestone + 2 Redstone Dust + 1 Nether Quartz => 1 Observer

Usage
The Observer block is a BUD (Block Update Detector) block that will send a short Redstone pulse if the block it is facing gets updated (mined, placed, etc.). They are placed like Pistons.



Trivia

 * BUD is a pre-existing concept in Minecraft: Pistons also feature BUD, and will get activated if a block near them is updated.
 * For example, if a block on the receiving end is set on Fire, the Piston will get activated. However this feature is currently only in MCPE.
 * Tommaso Checchi created a texture for the Observer Block, but it was rejected by Daniel Wustenhoff.
 * After Update 0.15.3 and Update 0.15.4, Observer Blocks are placed similarly to Pistons, due to complaints.
 * Piston BUDs do not work in PE because the developers replaced the quasi-connectivity bug with the Observer itself.