The Observer is a block that was added in Update 1.11. It is a BUD (Block Update Detector) and was a version exclusive to Pocket Edition until it was added to PC.
The Observer sends a Redstone signal every time a block that it is facing is updated.
- Once an update is detected, an Observer will send a one tick pulse, turning on and off.
- The Observer uses the texture that was rejected from Pocket Edition.
- Some updates can't be detected using an Observer on PE, and vice versa.
- The Observer can help make a Triple Piston Extender.